[lld][ELF] Fix error message

The error previously talked about a "section header" but was actually
referring to a program header.

Reviewed by: grimar, MaskRay

Differential Revision: https://reviews.llvm.org/D76846

Author: jh7370

lld/ELF/LinkerScript.cpp

@@ -1223,7 +1223,7 @@ std::vector<size_t> LinkerScript::getPhdrIndices(OutputSection *cmd) {
     if (Optional<size_t> idx = getPhdrIndex(phdrsCommands, s))
       ret.push_back(*idx);
     else if (s != "NONE")
-      error(cmd->location + ": section header '" + s +
+      error(cmd->location + ": program header '" + s +
             "' is not listed in PHDRS");
   }
   return ret;

lld/test/ELF/linkerscript/phdrs.s

@@ -128,7 +128,7 @@
 # DEFHDR-NEXT:      PF_X (0x1)
 # DEFHDR-NEXT:    ]
 
-# BADHDR:       {{.*}}.script:1: section header 'bar' is not listed in PHDRS
+# BADHDR:       {{.*}}.script:1: program header 'bar' is not listed in PHDRS
 
 # RUN: echo "PHDRS { text PT_LOAD FOOHDR; }" > %t1.script
 # RUN: not ld.lld -o /dev/null --script %t1.script %t 2>&1 | FileCheck --check-prefix=FOOHDR %s