Added options -cflag, -cxxflags, and -ldflags to override the default C

compilation, C++ compilation, and linker options.
e.g. This is the options I use for testing on my x86 iMac:
nice ./NightlyTest.pl -release -cflags "-Os -DNDEBUG -fomit-frame-pointer" -cxxflags "-Os -DNDEBUG -finline-functions -felide-constructors -fomit-frame-pointer"

llvm-svn: 26057