The current logic sets CCACHE_PREFIX to distcc when both distcc and
ccache are enabled. However, according to the source of ccache, it would
execute the command with execv, which would not look up arg0 from PATH,
unlike those exec functions with _p suffix.
This would result in the following error, when building a package with
both ccache and distcc enabled:
```
ccache: error: execute_noreturn of distcc failed: No such file or directory
```
This breaks package builds in different ways: packages that use make/cc
directly would yield the actual error which is the same as the above
line, packages that rely on other build systems wouldn't go through
compiler check and complain on a bad compiler.
To reproduce the problem, try to build a simple package:
```
git clone https://gitlab.archlinux.org/archlinux/packaging/packages/abc.git
cd abc
cp /etc/makepkg.conf .
echo 'BUILDENV=(distcc color ccache check !sign)' >> makepkg.conf
makepkg --config makepkg.conf
```
refs:
f887434d35/src/ccache/execute.cpp (L348)https://man.archlinux.org/man/exec.3.en#v_-_execv(),_execvp(),_execvpe()
Signed-off-by: Guoxin Pu <pugokushin@gmail.com>
680169fb61