I suspect the mbedtls programs to cause a lot of failed commits.
Currently, we see 66/500 commits fail in mbedtls.

During the historical build of cPython, I discovered that hashing of
vector operations was not implemented. Again this had no influence on
the incremental builds, since there was no chance to detect a change.

In C you can have extern definition and declaration in one place:

extern void foo() {
 ...
}

These must not be ignored.

Sometimes (I didn't search for the reason), the objectfile cache
handling was broken.

Since i suspect the bash overhead to be the reason for the overhead
observed in musl libc that made clang-hash slower than recompilation.

Too fool ccache, we add a spurious semi-colon in the global space. To
avoid warnings, which could slow down compilation, we have to suppress
the warnings and ignore the empty declaration in the visitor. The
warnings are only visible with -pedantic, which is no problem for the
data we have gathered so far.

ccache does not redo the compilation, if only a newline was added. But
a single semi-colon does do the trick.

Since we want to measure an end to end time, we have to use the
bare-mininum wrappers that only call clang with {nothing, ccache, clang-hash}