[NFC] Add explicit #include llvm-config.h where its macros are used, clang part.

(clang related part)
Without these explicit includes, removing other headers, who implicitly include llvm-config.h, may have non-trivial side effects.
For example, `clagd` may report even `llvm-config.h` as "no used" in case it defines a macro, that is expicitly used with #ifdef.
It is actually amplified with different build configs which use different set of macros.

Author: dfukalov

clang-tools-extra/clangd/Feature.cpp

@@ -8,6 +8,7 @@
 
 #include "Feature.h"
 #include "clang/Basic/Version.h"
+#include "llvm/Config/llvm-config.h" // for LLVM_ON_UNIX
 #include "llvm/Support/Compiler.h"
 #include "llvm/TargetParser/Host.h"
 

clang-tools-extra/clangd/unittests/ClangdTests.cpp

@@ -29,6 +29,7 @@
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Config/llvm-config.h" // for LLVM_ON_UNIX
 #include "llvm/Support/Allocator.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/Path.h"

clang-tools-extra/clangd/unittests/CompileCommandsTests.cpp

@@ -18,6 +18,7 @@
 #include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Config/llvm-config.h" // for LLVM_ON_UNIX
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Process.h"

clang-tools-extra/clangd/unittests/SerializationTests.cpp

@@ -12,6 +12,7 @@
 #include "support/Logger.h"
 #include "clang/Tooling/CompilationDatabase.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/Config/llvm-config.h" // for LLVM_ON_UNIX
 #include "llvm/Support/Compression.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/ScopedPrinter.h"

clang/include/clang/Interpreter/Value.h

@@ -33,6 +33,7 @@
 #ifndef LLVM_CLANG_INTERPRETER_VALUE_H
 #define LLVM_CLANG_INTERPRETER_VALUE_H
 
+#include "llvm/Config/llvm-config.h" // for LLVM_BUILD_LLVM_DYLIB, LLVM_BUILD_SHARED_LIBS
 #include "llvm/Support/Compiler.h"
 #include <cstdint>
 

clang/lib/Driver/ToolChains/Cuda.cpp

@@ -17,6 +17,7 @@
 #include "clang/Driver/InputInfo.h"
 #include "clang/Driver/Options.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/Config/llvm-config.h" // for LLVM_HOST_TRIPLE
 #include "llvm/Option/ArgList.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/FormatAdapters.h"

clang/lib/Driver/ToolChains/MinGW.cpp

@@ -15,6 +15,7 @@
 #include "clang/Driver/InputInfo.h"
 #include "clang/Driver/Options.h"
 #include "clang/Driver/SanitizerArgs.h"
+#include "llvm/Config/llvm-config.h" // for LLVM_HOST_TRIPLE
 #include "llvm/Option/ArgList.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"

clang/lib/Driver/ToolChains/WebAssembly.cpp

@@ -15,6 +15,7 @@
 #include "clang/Driver/Driver.h"
 #include "clang/Driver/DriverDiagnostic.h"
 #include "clang/Driver/Options.h"
+#include "llvm/Config/llvm-config.h" // for LLVM_VERSION_STRING
 #include "llvm/Option/ArgList.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"

clang/lib/Frontend/FrontendActions.cpp

@@ -26,6 +26,7 @@
 #include "clang/Serialization/ASTReader.h"
 #include "clang/Serialization/ASTWriter.h"
 #include "clang/Serialization/ModuleFile.h"
+#include "llvm/Config/llvm-config.h" // for LLVM_HOST_TRIPLE
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MemoryBuffer.h"

clang/tools/driver/driver.cpp

@@ -29,6 +29,7 @@
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringSet.h"
+#include "llvm/Config/llvm-config.h" // for LLVM_ON_UNIX
 #include "llvm/Option/ArgList.h"
 #include "llvm/Option/OptTable.h"
 #include "llvm/Option/Option.h"
@@ -52,6 +53,7 @@
 #include <optional>
 #include <set>
 #include <system_error>
+
 using namespace clang;
 using namespace clang::driver;
 using namespace llvm::opt;

clang/unittests/Driver/GCCVersionTest.cpp

@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "../../lib/Driver/ToolChains/Gnu.h"
+#include "llvm/Config/llvm-config.h" // for LLVM_BUILD_LLVM_DYLIB, LLVM_BUILD_SHARED_LIBS
 #include "gtest/gtest.h"
 
 // The Generic_GCC class is hidden in dylib/shared library builds, so