The clang API calls used by perf have changed in recent releases and
builds succeed with libclang-3.9 only. This introduces compatibility
with libclang-4.0 and above.

Without this patch, we will see the following compilation errors with
libclang-4.0+:

 util/c++/clang.cpp: In function ‘clang::CompilerInvocation* perf::createCompilerInvocation(llvm::opt::ArgStringList, llvm::StringRef&, clang::DiagnosticsEngine&)’:
 util/c++/clang.cpp:62:33: error: ‘IK_C’ was not declared in this scope
   Opts.Inputs.emplace_back(Path, IK_C);
                                  ^~~~
 util/c++/clang.cpp: In function ‘std::unique_ptr<llvm::Module> perf::getModuleFromSource(llvm::opt::ArgStringList, llvm::StringRef, llvm::IntrusiveRefCntPtr<clang::vfs::FileSystem>)’:
 util/c++/clang.cpp:75:26: error: no matching function for call to ‘clang::CompilerInstance::setInvocation(clang::CompilerInvocation*)’
   Clang.setInvocation(&*CI);
                           ^
 In file included from util/c++/clang.cpp:14:0:
 /usr/include/clang/Frontend/CompilerInstance.h:231:8: note: candidate: void clang::CompilerInstance::setInvocation(std::shared_ptr<clang::CompilerInvocation>)
    void setInvocation(std::shared_ptr<CompilerInvocation> Value);
         ^~~~~~~~~~~~~

Committer testing:

Tested on Fedora 27 after installing the clang-devel and llvm-devel
packages, versions:

  # rpm -qa | egrep llvm\|clang
  llvm-5.0.1-6.fc27.x86_64
  clang-libs-5.0.1-5.fc27.x86_64
  clang-5.0.1-5.fc27.x86_64
  clang-tools-extra-5.0.1-5.fc27.x86_64
  llvm-libs-5.0.1-6.fc27.x86_64
  llvm-devel-5.0.1-6.fc27.x86_64
  clang-devel-5.0.1-5.fc27.x86_64
  #

Make sure you don't have some older version lying around in /usr/local,
etc, then:

  $ make LIBCLANGLLVM=1 -C tools/perf install-bin

And in the end perf will be linked agains these libraries:

  # ldd ~/bin/perf | egrep -i llvm\|clang
	libclangAST.so.5 => /lib64/libclangAST.so.5 (0x00007f8bb2eb4000)
	libclangBasic.so.5 => /lib64/libclangBasic.so.5 (0x00007f8bb29e3000)
	libclangCodeGen.so.5 => /lib64/libclangCodeGen.so.5 (0x00007f8bb23f7000)
	libclangDriver.so.5 => /lib64/libclangDriver.so.5 (0x00007f8bb2060000)
	libclangFrontend.so.5 => /lib64/libclangFrontend.so.5 (0x00007f8bb1d06000)
	libclangLex.so.5 => /lib64/libclangLex.so.5 (0x00007f8bb1a3e000)
	libclangTooling.so.5 => /lib64/libclangTooling.so.5 (0x00007f8bb17d4000)
	libclangEdit.so.5 => /lib64/libclangEdit.so.5 (0x00007f8bb15c5000)
	libclangSema.so.5 => /lib64/libclangSema.so.5 (0x00007f8bb0cc9000)
	libclangAnalysis.so.5 => /lib64/libclangAnalysis.so.5 (0x00007f8bb0a23000)
	libclangParse.so.5 => /lib64/libclangParse.so.5 (0x00007f8bb0725000)
	libclangSerialization.so.5 => /lib64/libclangSerialization.so.5 (0x00007f8bb039a000)
	libLLVM-5.0.so => /lib64/libLLVM-5.0.so (0x00007f8bace98000)
	libclangASTMatchers.so.5 => /lib64/../lib64/libclangASTMatchers.so.5 (0x00007f8bab735000)
	libclangFormat.so.5 => /lib64/../lib64/libclangFormat.so.5 (0x00007f8bab4b2000)
	libclangRewrite.so.5 => /lib64/../lib64/libclangRewrite.so.5 (0x00007f8bab2a1000)
	libclangToolingCore.so.5 => /lib64/../lib64/libclangToolingCore.so.5 (0x00007f8bab08e000)
  #
Signed-off-by: Sandipan Das <sandipan@linux.vnet.ibm.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Fixes: 00b86691 ("perf clang: Add builtin clang support ant test case")
Link: http://lkml.kernel.org/r/20180404180419.19056-2-sandipan@linux.vnet.ibm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>