[crt] Use CMAKE_C_COMPILER_ARG1 in compiler invocation

[phosek]

Summary

This is needed when using compiler wrappers such as ccache or distcc
and should address the failure on clang-x86_64-debian-fast bot.

[thakis]

As said on IRC, a nicer fix would be to make clang-x86_64-debian-fast and friends use use CMAKE_C_COMPILER_LAUNCHER / CMAKE_CXX_COMPILER_LAUNCHER for ccache instead of setting CC / CXX – but it's also good to make the pre-cmake-3.4 way of configuring this work.

compiler-rt/trunk/cmake/Modules/AddCompilerRT.cmake

if(type STREQUAL "OBJECT")
       endif()
       if(CMAKE_SYSROOT)
         list(APPEND extra_cflags_${libname} "--sysroot=${CMAKE_SYSROOT}")
       endif()
       string(REPLACE ";" " " extra_cflags_${libname} "${extra_cflags_${libname}}")
       string(REGEX MATCHALL "<[A-Za-z0-9_]*>" substitutions
              ${CMAKE_C_COMPILE_OBJECT})
       set(compile_command_${libname} "${CMAKE_C_COMPILE_OBJECT}")
+
       set(output_file_${libname} ${output_name_${libname}}${CMAKE_C_OUTPUT_EXTENSION})
       foreach(substitution ${substitutions})
         if(substitution STREQUAL "<CMAKE_C_COMPILER>")
-          string(REPLACE "<CMAKE_C_COMPILER>" "${CMAKE_C_COMPILER}"
+          string(REPLACE "<CMAKE_C_COMPILER>" "${CMAKE_C_COMPILER} ${CMAKE_C_COMPILER_ARG1}"
                  compile_command_${libname} ${compile_command_${libname}})
         elseif(substitution STREQUAL "<OBJECT>")
           string(REPLACE "<OBJECT>" "${output_dir_${libname}}/${output_file_${libname}}"
                  compile_command_${libname} ${compile_command_${libname}})
         elseif(substitution STREQUAL "<SOURCE>")
           string(REPLACE "<SOURCE>" "${sources_${libname}}"
                  compile_command_${libname} ${compile_command_${libname}})
         elseif(substitution STREQUAL "<FLAGS>")

compiler-rt/trunk/lib/crt/CMakeLists.txt

if(CMAKE_C_COMPILER_ID MATCHES Clang AND CMAKE_C_COMPILER_TARGET)
     list(APPEND try_compile_flags "-target ${CMAKE_C_COMPILER_TARGET}")
   endif()
 
   string(REPLACE ";" " " extra_flags "${try_compile_flags}")
 
   set(test_compile_command "${CMAKE_C_COMPILE_OBJECT}")
   foreach(substitution ${substitutions})
     if(substitution STREQUAL "<CMAKE_C_COMPILER>")
-      string(REPLACE "<CMAKE_C_COMPILER>"
-             "${CMAKE_C_COMPILER}" test_compile_command ${test_compile_command})
+      string(REPLACE "<CMAKE_C_COMPILER>" "${CMAKE_C_COMPILER} ${CMAKE_C_COMPILER_ARG1}"
+             test_compile_command ${test_compile_command})
     elseif(substitution STREQUAL "<OBJECT>")
       string(REPLACE "<OBJECT>" "${TARGET_NAME}/CheckSectionExists.o"
              test_compile_command ${test_compile_command})
     elseif(substitution STREQUAL "<SOURCE>")
       string(REPLACE "<SOURCE>" "${TARGET_NAME}/CheckSectionExists.c"
              test_compile_command ${test_compile_command})
     elseif(substitution STREQUAL "<FLAGS>")
       string(REPLACE "<FLAGS>" "${CMAKE_C_FLAGS} ${extra_flags}"