cmake: improve the PCH support detection

Author: illwieckz

CMakeLists.txt

@@ -415,7 +415,9 @@ function(ADD_PRECOMPILED_HEADER Target)
     set(Header ${COMMON_DIR}/Common.h)
 
     # Compiler-specific PCH support
-    if (CMAKE_COMPILER_IS_GNUCXX OR "${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang" OR NACL)
+    try_c_cxx_flag(PCH "-pch")
+
+    if (PCH)
         add_custom_command(OUTPUT "${OBJ_DIR}/${Target}.h.gch"
             COMMAND ${PNACLPYTHON_PREFIX2} ${CMAKE_CXX_COMPILER} ${Defs} ${Flags} -x c++-header ${Header} -o "${OBJ_DIR}/${Target}.h.gch"
             DEPENDS ${Header}
@@ -426,7 +428,7 @@ function(ADD_PRECOMPILED_HEADER Target)
         add_dependencies(${Target} ${Target}-pch)
 
         # PNaCl clang doesn't support -include-pch properly
-        if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang" AND NOT NACL)
+        if (NOT DAEMON_CXX_COMPILER_NAME STREQUAL "PNaCl")
             set_property(TARGET ${Target} APPEND PROPERTY COMPILE_OPTIONS "-include-pch;${OBJ_DIR}/${Target}.h.gch")
         else()
             set_property(TARGET ${Target} APPEND PROPERTY COMPILE_OPTIONS "-include;${OBJ_DIR}/${Target}.h;-Winvalid-pch")