Rather than setting them in the build profile, just set them in
etc/defaults.conf (overridable via etc/conf) to simplify the code.
- Also enable _FORTIFY_SOURCE=2 in CPPFLAGS.
- Also enable -z,relro in LDFLAGS.
As suggested by @chneukirchen.
common/build-profiles contains the compilation flags used in native
builds, and are defined per architecture:
- x86_64 (glibc)
- x86_64-musl (musl)
If XBPS_CFLAGS or XBPS_CXXFLAGS are set in `etc/conf`, the settings
from the build profile will be overrided.