environment: Pass defines to clang based ObjC[++] compilers
environment: Pass defines to clang based ObjC[++] compilers

mypy noticed that we were passing [] (instead of a dict or None) to the
ClangCompiler class in objc, which made me noticed that for C and C++ we
set the defines, but not for ObjC and ObjC++

QuLogic/meson,jpakkane/meson,mesonbuild/meson,mesonbuild/meson,mesonbuild/meson,pexip/meson,QuLogic/meson,mesonbuild/meson,mesonbuild/meson,jpakkane/meson,jpakkane/meson,jpakkane/meson,pexip/meson,QuLogic/meson,pexip/meson,mesonbuild/meson,mesonbuild/meson,QuLogic/meson,mesonbuild/meson,mesonbuild/meson,QuLogic/meson,pexip/meson,jpakkane/meson,pexip/meson,QuLogic/meson,jpakkane/meson,mesonbuild/meson,pexip/meson,QuLogic/meson,pexip/meson,pexip/meson,jpakkane/meson,QuLogic/meson,pexip/meson,jpakkane/meson,jpakkane/meson,QuLogic/meson,pexip/meson