libhsakmt: Disable -Werror by default

This can cause build failures on unknown of future compiler versions.
Only enable it if explicitly enabled by an environment variable. This
allows us to continue building with -Werror in internal builds with
known compiler versions.

Change-Id: Ic1cd9d223218cc4e4cddba49df93bb357c1cbd40
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>

CMakeLists.txt

@@ -67,7 +67,7 @@ set (HSAKMT_C_FLAGS -fPIC -W -Wall -Wextra -Wno-unused-parameter -Wformat-securi
 if ( CMAKE_COMPILER_IS_GNUCC )
     set ( HSAKMT_C_FLAGS "${HSAKMT_C_FLAGS}" -Wlogical-op)
 endif ()
-if ( "${CMAKE_C_COMPILER_VERSION}" STRGREATER "4.8.0")
+if ( ${HSAKMT_WERROR} )
     set ( HSAKMT_C_FLAGS "${HSAKMT_C_FLAGS}" -Werror )
 endif ()
 if ( "${CMAKE_BUILD_TYPE}" STREQUAL Release )