* it is now -fcompiler-rt and -fno-compiler-rt to override the (quite
reasonable) default of bundling compiler-rt only for executables and
dynamic libraries.
- the build.zig API is still called bundle_compiler_rt however it is
now an optional bool instead of a bool. leaving it as `null` means
to use the compiler default.
* renamed some internal identifiers to make the source more readable
* additionally support -fcompiler-rt when doing build-obj for ELF files
since that target already supports linking multiple objects into one.
- includes an error message when attempting this for non-ELF. in the
future this could additionally be supported with a more advanced
implementation that does not rely on the linker.
* properly populate the linker cache hash
ff9798eb26