Build system should honor CC, CFLAGS, CXX, CXXFLAGS

[fweimer]

Build systems for native binaries should honor the environment variables CC, CFLAGS, CXX, CXXFLAGS, LDFLAGS and pass them to compiler and linker invocations.

The idea is that it should be easy to enable special build features like Address Sanitizier, or to comply with distribution hardening best practices.

If these variables are set, they should not override critical flags required by the existing build system.

[david-a-wheeler]

Here's a proposed tweak:

Build systems for native binaries SHOULD honor the relevant compiler and linker environment variables passed in to them (e.g., CC, CFLAGS, CXX, CXXFLAGS, and LDFLAGS) and pass them to compiler and linker invocations. A build system MAY extend them with additional flags; it SHOULD NOT simply replace provided values with its own.
DETAILS: It should be easy to enable special build features like Address Sanitizier (ASAN), or to comply with distribution hardening best practices (e.g., by easily turning on compiler flags to do so).

[fweimer]

Colin Walters had the same idea: https://github.com/cgwalters/build-api

[david-a-wheeler]

I've added this as a proposed criterion for the "passing+1" badge level (making it a MUST).