Add a CFLAGS_EXTRAS make variable to be able to pass things (like...

Add a CFLAGS_EXTRAS make variable to be able to pass things (like '-DTEST_BLOCK_CAPTURED_VARS') to the compile phase.

Plus add a DYLIB_ONLY make variable that can be used to turn off compilation/building of a.out. Example:

[16:39:21] johnny:/Volumes/data/lldb/svn/trunk/test/lang/c/global_variables $ make clean
rm -rf "a.out" "a.out.dSYM"  main.o main.d a.o a.d liba.dylib liba.dylib.dSYM
[16:39:24] johnny:/Volumes/data/lldb/svn/trunk/test/lang/c/global_variables $ make DYLIB_ONLY=YES
clang -gdwarf-2 -O0   -arch x86_64   -c -o a.o a.c
clang -gdwarf-2 -O0   -arch x86_64  a.o -install_name "@executable_path/liba.dylib" -dynamiclib -o "liba.dylib"
[16:39:30] johnny:/Volumes/data/lldb/svn/trunk/test/lang/c/global_variables $

llvm-svn: 147821