CMakeLists changes to make thunk buildable on CentOS 6.9

Removed Werror CFLAGS for lower version of gcc. there
will be some warning message on lower gcc version but build
is ok.

Signed-off-by: Oak Zeng <Oak.Zeng@amd.com>

Change-Id: Icf556625cb870c4ad73e1d89f3d4ade3a96e821f

CMakeLists.txt

@@ -53,7 +53,11 @@ set ( BUILD_VERSION_STRING "${BUILD_VERSION_MAJOR}.${BUILD_VERSION_MINOR}.${BUIL
 set ( CMAKE_VERBOSE_MAKEFILE on )
 
 ## Compiler flags
-set ( CMAKE_C_FLAGS "-fPIC -W -Wall -Wextra -Werror -Wno-unused-parameter -Wformat-security -Wswitch-default -Wundef -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-qual -Wlogical-op -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wredundant-decls -Wunreachable-code -std=gnu99 -fvisibility=hidden -O2" )
+set ( CMAKE_C_FLAGS "-fPIC -W -Wall -Wextra -Wno-unused-parameter -Wformat-security -Wswitch-default -Wundef -Wshadow -Wpointer-arith -Wbad-function-cast -Wcast-qual -Wlogical-op -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wredundant-decls -Wunreachable-code -std=gnu99 -fvisibility=hidden -O2" )
+if ( "${CMAKE_C_COMPILER_VERSION}" STRGREATER "4.8.0")
+    set ( CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Werror" )
+endif ()
+
 
 set ( HSAKMT_LINKER_SCRIPT "${CMAKE_CURRENT_SOURCE_DIR}/src/libhsakmt.ver" )