[llvm-objdump] Use "--" for long options in --help text

Single dash for these options is not recognised.

Changes found by running this on the --help output
and the user guide:
grep -e ' -[a-zA-Z]\{2,\}'

The user guide was updated in https://reviews.llvm.org/D92305
so no change there.

Reviewed By: jhenderson, MaskRay

Differential Revision: https://reviews.llvm.org/D92310

Author: DavidSpickett

llvm/tools/llvm-objdump/MachODump.cpp

@@ -107,70 +107,70 @@ static cl::opt<bool> NoLeadingHeaders("no-leading-headers",
 
 cl::opt<bool> objdump::UniversalHeaders(
     "universal-headers",
-    cl::desc("Print Mach-O universal headers (requires -macho)"),
+    cl::desc("Print Mach-O universal headers (requires --macho)"),
     cl::cat(MachOCat));
 
 static cl::opt<bool> ArchiveMemberOffsets(
     "archive-member-offsets",
     cl::desc("Print the offset to each archive member for Mach-O archives "
-             "(requires -macho and -archive-headers)"),
+             "(requires --macho and --archive-headers)"),
     cl::cat(MachOCat));
 
 cl::opt<bool> objdump::IndirectSymbols(
     "indirect-symbols",
     cl::desc(
-        "Print indirect symbol table for Mach-O objects (requires -macho)"),
+        "Print indirect symbol table for Mach-O objects (requires --macho)"),
     cl::cat(MachOCat));
 
 cl::opt<bool> objdump::DataInCode(
     "data-in-code",
     cl::desc(
-        "Print the data in code table for Mach-O objects (requires -macho)"),
+        "Print the data in code table for Mach-O objects (requires --macho)"),
     cl::cat(MachOCat));
 
 cl::opt<bool>
     objdump::LinkOptHints("link-opt-hints",
                           cl::desc("Print the linker optimization hints for "
-                                   "Mach-O objects (requires -macho)"),
+                                   "Mach-O objects (requires --macho)"),
                           cl::cat(MachOCat));
 
 cl::opt<bool>
     objdump::InfoPlist("info-plist",
                        cl::desc("Print the info plist section as strings for "
-                                "Mach-O objects (requires -macho)"),
+                                "Mach-O objects (requires --macho)"),
                        cl::cat(MachOCat));
 
 cl::opt<bool>
     objdump::DylibsUsed("dylibs-used",
                         cl::desc("Print the shared libraries used for linked "
-                                 "Mach-O files (requires -macho)"),
+                                 "Mach-O files (requires --macho)"),
                         cl::cat(MachOCat));
 
 cl::opt<bool> objdump::DylibId("dylib-id",
                                cl::desc("Print the shared library's id for the "
-                                        "dylib Mach-O file (requires -macho)"),
+                                        "dylib Mach-O file (requires --macho)"),
                                cl::cat(MachOCat));
 
 static cl::opt<bool>
     NonVerbose("non-verbose",
                cl::desc("Print the info for Mach-O objects in non-verbose or "
-                        "numeric form (requires -macho)"),
+                        "numeric form (requires --macho)"),
                cl::cat(MachOCat));
 
 cl::opt<bool>
     objdump::ObjcMetaData("objc-meta-data",
                           cl::desc("Print the Objective-C runtime meta data "
-                                   "for Mach-O files (requires -macho)"),
+                                   "for Mach-O files (requires --macho)"),
                           cl::cat(MachOCat));
 
 static cl::opt<std::string> DisSymName(
     "dis-symname",
-    cl::desc("disassemble just this symbol's instructions (requires -macho)"),
+    cl::desc("disassemble just this symbol's instructions (requires --macho)"),
     cl::cat(MachOCat));
 
 static cl::opt<bool> NoSymbolicOperands(
     "no-symbolic-operands",
-    cl::desc("do not symbolic operands when disassembling (requires -macho)"),
+    cl::desc("do not symbolic operands when disassembling (requires --macho)"),
     cl::cat(MachOCat));
 
 static cl::list<std::string>

llvm/tools/llvm-objdump/llvm-objdump.cpp

@@ -101,7 +101,7 @@ static cl::alias AllHeadersShort("x", cl::desc("Alias for --all-headers"),
 static cl::opt<std::string>
     ArchName("arch-name",
              cl::desc("Target arch to disassemble for, "
-                      "see -version for available targets"),
+                      "see --version for available targets"),
              cl::cat(ObjdumpCat));
 
 cl::opt<bool>
@@ -274,7 +274,7 @@ static cl::alias PrivateHeadersShort("p",
 cl::list<std::string>
     objdump::FilterSections("section",
                             cl::desc("Operate on the specified sections only. "
-                                     "With -macho dump segment,section"),
+                                     "With --macho dump segment,section"),
                             cl::cat(ObjdumpCat));
 static cl::alias FilterSectionsj("j", cl::desc("Alias for --section"),
                                  cl::NotHidden, cl::Grouping, cl::Prefix,
@@ -303,7 +303,7 @@ static cl::opt<bool> PrintSource(
     cl::desc(
         "Display source inlined with disassembly. Implies disassemble object"),
     cl::cat(ObjdumpCat));
-static cl::alias PrintSourceShort("S", cl::desc("Alias for -source"),
+static cl::alias PrintSourceShort("S", cl::desc("Alias for --source"),
                                   cl::NotHidden, cl::Grouping,
                                   cl::aliasopt(PrintSource));
 
@@ -335,11 +335,11 @@ static cl::alias DynamicSymbolTableShort("T",
                                          cl::NotHidden, cl::Grouping,
                                          cl::aliasopt(DynamicSymbolTable));
 
-cl::opt<std::string> objdump::TripleName(
-    "triple",
-    cl::desc(
-        "Target triple to disassemble for, see -version for available targets"),
-    cl::cat(ObjdumpCat));
+cl::opt<std::string>
+    objdump::TripleName("triple",
+                        cl::desc("Target triple to disassemble for, see "
+                                 "--version for available targets"),
+                        cl::cat(ObjdumpCat));
 
 cl::opt<bool> objdump::UnwindInfo("unwind-info",
                                   cl::desc("Display unwind information"),