[Issue 15012] Druntime Makefile whitelists compilers

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=15012

--- Comment #3 from github-bugzilla at puremagic.com ---
Commit pushed to master at https://github.com/D-Programming-Language/phobos

https://github.com/D-Programming-Language/phobos/commit/0bfc7ca32f074ff4295f567033da4f72b4d377a7
remove CC filter for CFLAGS

- allows to use compiler wrappers
- fixes make CC=/path/to/cc
- fixes Issue 15012
- still can be overriden with make CFLAGS=

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