build: more portable Makefile

• Make some $(shell) calls lazy
• $(wildcard) instead of ls
• $(info) instead of echo
• $? instead of duplicated file lists

Biggest benefit: smoother experience with MSYS make (can be added to "Git Bash", or vendored)

/CC @nodejs/build-files @nodejs/platform-windows

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines