Don't warn for empty 'if' body if there is a macro that expands to nothing, e.g:
tree1c8c6e68f978b9b156704e77c31beb8bf573b845
-rw-r--r-- 4909 CMakeLists.txt
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-rw-r--r-- 2335 Makefile
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-rw-r--r-- 3307 TODO.txt
drwxr-xr-x - bindings
drwxr-xr-x - clang.xcodeproj
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drwxr-xr-x - examples
drwxr-xr-x - include
drwxr-xr-x - lib
drwxr-xr-x - runtime
drwxr-xr-x - test
drwxr-xr-x - tools
drwxr-xr-x - utils
drwxr-xr-x - www