compiledb should regroup all -D and -I option together (vscode doesn't like that when they are not)

[ykoehler]

using a command line such as

gcc -DSTUFF=1 -O2 -DMORE_STUFF=1 -o file.o file.c

result in the same pattern in the compile_commands and vscode doesn't like that, it would be great to have a vscode compatible mode where the above gets converted to

gcc -O2 -DSTUFF=1 -DMORE_STUFF=1 -o file.o file.c