Removing __linux__ definition in CMake

Removing this definition as this should already be defined by compiler.
This is causing compile errors on newer versions of llvm because the
macro is being redefined.

Change-Id: Ica6a06f46a14e16d3f52e83b9b5ee8cfd7359510

runtime/hsa-runtime-tools/CMakeLists.txt

@@ -22,7 +22,7 @@ list ( APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/../cmake_modules" )
 include ( utils )
 
 ## Compiler preproc definitions.
-add_definitions ( -D__linux__ )
+#add_definitions ( -D__linux__ )
 add_definitions ( -DUNIX_OS )
 add_definitions ( -DLINUX )
 add_definitions ( -D__AMD64__ )