Add compiler target compile options.

For clang, this allows passing -target <triple> to the compiler, and
for qcc, -V<arch> using toolchain files containing something like

 set(triple arm-linux-gnueabihf)
 set(CMAKE_C_COMPILER "/usr/bin/clang")
 set(CMAKE_C_COMPILER_TARGET ${triple})
 set(CMAKE_CXX_COMPILER "/usr/bin/clang++")
 set(CMAKE_CXX_COMPILER_TARGET ${triple})

or

 set(arch gcc_ntoarmv7le)
 set(CMAKE_C_COMPILER /opt/qnx650/host/linux/x86/usr/bin/qcc)
 set(CMAKE_C_COMPILER_TARGET ${arch})
 set(CMAKE_CXX_COMPILER /opt/qnx650/host/linux/x86/usr/bin/QCC)
 set(CMAKE_CXX_COMPILER_TARGET ${arch})

Both clang and qcc are inherently cross compiler( driver)s.

Modules/CMakeDetermineCompilerABI.cmake

@@ -28,6 +28,9 @@ function(CMAKE_DETERMINE_COMPILER_ABI lang src)
     if(DEFINED CMAKE_${lang}_VERBOSE_FLAG)
       set(CMAKE_FLAGS "-DCMAKE_EXE_LINKER_FLAGS=${CMAKE_${lang}_VERBOSE_FLAG}")
     endif()
+    if(CMAKE_${lang}_COMPILER_TARGET)
+      set(CMAKE_FLAGS "${CMAKE_FLAGS} -DCMAKE_${lang}_COMPILER_TARGET=${CMAKE_${lang}_COMPILER_TARGET}")
+    endif()
     try_compile(CMAKE_${lang}_ABI_COMPILED
       ${CMAKE_BINARY_DIR} ${src}
       CMAKE_FLAGS "${CMAKE_FLAGS}"

Modules/Compiler/Clang.cmake

@@ -25,4 +25,5 @@ macro(__compiler_clang lang)
   set(CMAKE_${lang}_COMPILE_OPTIONS_PIE "-fPIE")
   set(CMAKE_INCLUDE_SYSTEM_FLAG_${lang} "-isystem ")
   set(CMAKE_${lang}_COMPILE_OPTIONS_VISIBILITY "-fvisibility=")
+  set(CMAKE_${lang}_COMPILE_OPTION_TARGET "-target ")
 endmacro()

Modules/Platform/QNX.cmake

@@ -13,6 +13,9 @@ set(CMAKE_SHARED_LIBRARY_RUNTIME_C_FLAG_SEP ":")
 set(CMAKE_SHARED_LIBRARY_RPATH_LINK_C_FLAG "-Wl,-rpath-link,")
 set(CMAKE_SHARED_LIBRARY_SONAME_C_FLAG "-Wl,-soname,")
 set(CMAKE_EXE_EXPORTS_C_FLAG "-Wl,--export-dynamic")
+# http://www.qnx.com/developers/docs/6.4.0/neutrino/utilities/q/qcc.html#examples
+set(CMAKE_C_COMPILE_OPTION_TARGET "-V")
+set(CMAKE_CXX_COMPILE_OPTION_TARGET "-V")
 
 # Shared libraries with no builtin soname may not be linked safely by
 # specifying the file path.

Source/cmLocalGenerator.cxx

@@ -1044,11 +1044,20 @@ cmLocalGenerator::ExpandRuleVariable(std::string const& variable,
       // If this is the compiler then look for the extra variable
       // _COMPILER_ARG1 which must be the first argument to the compiler
       const char* compilerArg1 = 0;
+      const char* compilerTarget = 0;
+      const char* compilerOptionTarget = 0;
       if(actualReplace == "CMAKE_${LANG}_COMPILER")
         {
         std::string arg1 = actualReplace + "_ARG1";
         cmSystemTools::ReplaceString(arg1, "${LANG}", lang);
         compilerArg1 = this->Makefile->GetDefinition(arg1.c_str());
+        compilerTarget
+              = this->Makefile->GetDefinition(
+                (std::string("CMAKE_") + lang + "_COMPILER_TARGET").c_str());
+        compilerOptionTarget
+              = this->Makefile->GetDefinition(
+                (std::string("CMAKE_") + lang +
+                                          "_COMPILE_OPTION_TARGET").c_str());
         }
       if(actualReplace.find("${LANG}") != actualReplace.npos)
         {
@@ -1069,6 +1078,11 @@ cmLocalGenerator::ExpandRuleVariable(std::string const& variable,
             ret += " ";
             ret += compilerArg1;
             }
+          if (compilerTarget && compilerOptionTarget)
+            {
+            ret += compilerOptionTarget;
+            ret += compilerTarget;
+            }
           return ret;
           }
         return replace;