Support building on RHEL 8.0

Those changes add support for building on RHEL 8.X while preserving
compatibility with other build environments.

Adds:
 - More advanced support for outside-of-system gcc installation
 - Links with proper runtime in case of gcc installation used for
   building is different from the system default one.

Author: Vladislav Aranov

meson.build

@@ -28,6 +28,8 @@ add_project_arguments(
   ], language: 'cpp'
 )
 
+fs = import('fs')
+
 # For debug builds, we want every debug info we can get plus addrsan.
 buildtype = get_option('buildtype')
 if buildtype == 'debug' or buildtype == 'debugoptimized'
@@ -48,22 +50,52 @@ gcc = find_program('gcc', version : '>=7.5.0')
 # building with the correct headers, otherwise we run the risk of building
 # clang-extract with different headers than libLLVM
 gcc_install_dir = ''
-gcc_output = run_command(gcc.full_path(), '-v', check: true).stderr().strip().split('\n')
-foreach line : gcc_output
-  params = line.split('=')
-  lhs = params.get(0)
-  rhs = params.get(1, '')
+build_dir_absolute_path = meson.build_root()
+simple_program_file = configure_file(output: 'simple_program.c', input: 'simple_program.c.in', copy: true )
 
-  if lhs == 'COLLECT_LTO_WRAPPER'
-    gcc_install_dir = run_command('dirname', rhs, check: true).stdout().strip()
-    break
+gcc_output = run_command(gcc.full_path(), '-v', '-o', build_dir_absolute_path / 'simple_program.out',
+                         build_dir_absolute_path / 'simple_program.c', check: true).stderr().strip().split('\n')
+foreach line : gcc_output
+  if line.contains('crtbegin.o')
+    ilines = line.strip().split(' ')
+    foreach iline : ilines
+      if iline.contains('crtbegin.o')
+        gcc_install_dir = fs.parent(iline)
+        break
+      endif
+    endforeach
   endif
 endforeach
+if build_machine.system() == 'linux'
+  rm = find_program('rm')
+  run_command(rm.full_path(),'-f', build_dir_absolute_path / 'simple_program.out', check: false)
+endif
 
 # Check if we got the gcc installation dir and add it to the project arguments.
 assert(gcc_install_dir != '', 'GCC headers dir not found. Check \'gcc -v\'')
 add_project_arguments('--gcc-install-dir=' + gcc_install_dir, language: 'cpp')
 
+########## Dependency: additional clang includes ################
+llvm_config = find_program('llvm-config')
+if llvm_config.found()
+  extra_args_line = run_command(llvm_config.full_path(), '--cxxflags').stdout().strip().split('\n')[0]
+  extra_args = extra_args_line.split(' -')
+  i = 0
+  foreach arg : extra_args
+    targ = arg
+    if i > 0
+      targ = '-' + arg
+    endif
+    if(not targ.startswith('-I'))
+      i += 1
+      continue
+    endif
+    message('Adding extra compilation flag: ' + targ)
+    add_project_arguments(targ, language: 'cpp')
+    i += 1
+  endforeach
+endif
+
 ########## Dependency: clang libraries ################
 llvm_libdir = dependency('llvm', version : '>=16').get_variable(cmake : 'LLVM_LIBRARY_DIR', configtool: 'libdir')
 
@@ -82,13 +114,15 @@ incdir = include_directories('libcextract')
 executable('ce-inline', 'Inline.cpp',
   include_directories : incdir,
   install : true,
+  link_args : ['--gcc-install-dir=' + gcc_install_dir],
   link_with : libcextract_static,
   dependencies : [elf_dep, zlib_dep, zstd_dep]
 )
 
 executable('clang-extract', 'Main.cpp',
   include_directories : incdir,
   install : true,
+  link_args : ['--gcc-install-dir=' + gcc_install_dir],
   link_with : libcextract_static,
   dependencies : [elf_dep, clang_dep, zlib_dep, zstd_dep]
 )

simple_program.c.in

@@ -0,0 +1 @@
+int main(){return 0;}