native/make/osx: circumvent unavailable gobjcopy

It's not used anyways, so just create an empty hex file if gobjcopy is
not found.
dist/tools/cppcheck: add license
dist/tools/externc: add license
dist/tools/licenses: add license
Merge pull request #2115 from LudwigOrtmann/ci-scripts-licenses

Ci scripts licenses
Merge pull request #2114 from LudwigOrtmann/native-osx-gobjcopy

native/make/osx: circumvent unavailable gobjcopy