Don't check VERSION_BUILD is defined

Check if it is true or not. The string() call would define this to an
empty string, which would pass. This would then leave a trailing -
in the version string, which dpkg would error on during package
installation.

Change-Id: Ifb5fc15f5dde506e96bff7881a5d3f22d983406e


[ROCm/ROCR-Runtime commit: 0016c6ce5b]

projects/rocr-runtime/runtime/hsa-runtime/cmake_modules/utils.cmake

@@ -73,7 +73,7 @@ function( parse_version VERSION_STRING )
         set ( TEMP_VERSION_STRING "${TEMP_VERSION_STRING}.${PATCH}" )
     endif ()
 
-    if ( DEFINED VERSION_BUILD )
+    if ( VERSION_BUILD )
         set ( VERSION_BUILD "${VERSION_BUILD}" PARENT_SCOPE )
     endif ()