Remove ccache wrappers

Remove ccache wrappers

These wrappers are not needed as CC doesn't need to be a single word.

a53b084e497a9f1629a2caada833ebe14a6838b7 which introduced the wrappers
doesn't explain why they were really needed and why only for the target
and not for the host.

Moreover, name of the wrappers breaks a ccache assumption: since
v4.0-3-g6a92b4cd3a67 it has special handling for "chained" invocation
such as "ccache ccache gcc" where it skips all the "ccache*" names in
the middle and proceeds to run as if it was started as "ccache
gcc"[1][2].

This becomes important when a build system sees ccache in the PATH and
automatically enables it by prepending to CC. An example of such a
system would be autosetup as used by jimtcl. With the wrappers it breaks
as the command line ends up being just "ccache -Os..." because
"ccache_cc" gets skipped as it starts with "ccache".

[1] https://github.com/ccache/ccache/blob/master/src/ccache.cpp#L2105
[2] https://github.com/ccache/ccache/blob/master/src/Util.cpp#L802

Reported-by: Karl Palsson <karlp@etactica.com>
Signed-off-by: Paul Fertser <fercerpav@gmail.com>