Build fix for older clang compilers.

Per clang 13 option -Wno-error=unused-but-set-variable is not
recoginized nor is the diagnostic emitted.  Set this option
conditional to the clang compiler version.

Change-Id: I3c0958dffa985d53b641f9eff4e702988dffd033

runtime/hsa-runtime/CMakeLists.txt

@@ -126,16 +126,19 @@ target_include_directories( ${CORE_RUNTIME_TARGET}
 set_property(TARGET ${CORE_RUNTIME_TARGET} PROPERTY INSTALL_RPATH "$ORIGIN;$ORIGIN/../../lib;$ORIGIN/../../lib64;$ORIGIN/../lib64" )
 
 ## ------------------------- Linux Compiler and Linker options -------------------------
-set ( HSA_CXX_FLAGS ${HSA_COMMON_CXX_FLAGS} -Werror -fexceptions -fno-rtti -fvisibility=hidden -Wno-error=missing-braces -Wno-error=sign-compare -Wno-sign-compare -Wno-write-strings -Wno-conversion-null -fno-math-errno -fno-threadsafe-statics -fmerge-all-constants -fms-extensions -Wno-error=comment -Wno-comment -Wno-error=pointer-arith -Wno-pointer-arith -Wno-error=unused-variable -Wno-error=unused-function -Wno-error=unused-but-set-variable )
+set ( HSA_CXX_FLAGS ${HSA_COMMON_CXX_FLAGS} -Werror -fexceptions -fno-rtti -fvisibility=hidden -Wno-error=missing-braces -Wno-error=sign-compare -Wno-sign-compare -Wno-write-strings -Wno-conversion-null -fno-math-errno -fno-threadsafe-statics -fmerge-all-constants -fms-extensions -Wno-error=comment -Wno-comment -Wno-error=pointer-arith -Wno-pointer-arith -Wno-error=unused-variable -Wno-error=unused-function )
 
 ## Extra image settings - audit!
 set ( HSA_CXX_FLAGS ${HSA_CXX_FLAGS} -Wno-deprecated-declarations )
 
 if ( CMAKE_COMPILER_IS_GNUCXX )
-    set ( HSA_CXX_FLAGS ${HSA_CXX_FLAGS} -Wno-error=maybe-uninitialized)
+    set ( HSA_CXX_FLAGS ${HSA_CXX_FLAGS} -Wno-error=maybe-uninitialized -Wno-error=unused-but-set-variable)
 endif ()
 if ( CMAKE_CXX_COMPILER_ID MATCHES "Clang")
   set ( HSA_CXX_FLAGS ${HSA_CXX_FLAGS} -Wno-error=self-assign)
+  if( CLANG_VERSION_MAJOR -ge 13)
+    set ( HSA_CXX_FLAGS ${HSA_CXX_FLAGS} -Wno-error=unused-but-set-variable)
+  endif()
 endif()
 
 set ( DRVDEF "${CMAKE_CURRENT_SOURCE_DIR}/hsacore.so.def" )