Regression caused by 51a836bf commit

Commit 51a836bf recently was cherry-picked by Debian. Now it is in Ubuntu and causes Compiz build failure.

Build fails with:
<command-line>: error: missing terminating " character [-Werror]

Define flags are now:
-D'DUMMY_CONF_PATH=\"/usr/share/xorg/gtest/dummy.conf\"' -D'LOGFILE_DIR=\"/tmp\"'

But used to be:
-DDUMMY_CONF_PATH=\"/usr/share/xorg/gtest/dummy.conf\" -DLOGFILE_DIR=\"/tmp\"

@whot Can you comment why that change was needed?