Replace error-prone superenv debug ouput with a separate log file

superenv's debug output tends to break things, there is no reliable way to detect where it will break things, and I'm tired of hacking around it just find yet another place where it is broken. If we have to fix a bunch of individual formula just to make this work, then superenv doesn't "just work". So let's replace it with a separate log file that doesn't interfere with builds.

For every regular build log file (like `02.make`) there is a corresponding cc log file (`02.make.cc`).

Each invocation produces an entry in the file that looks like this:

```
clang called with: -g -O2 -DHAVE_CONFIG_H -DTIG_VERSION="1.2.1" -DSYSCONFDIR="/usr/local/etc" -c -o tig.o tig.c
superenv removed:  -g -O2
superenv added:    -pipe -w -Os -march=native -isystem/usr/local/include -isystem/usr/include/libxml2 -isystem/System/Library/Frameworks/OpenGL.framework/Versions/Current/Headers
superenv executed: clang -pipe -w -Os -march=native -DHAVE_CONFIG_H -DTIG_VERSION="1.2.1" -DSYSCONFDIR="/usr/local/etc" -c -o tig.o tig.c -isystem/usr/local/include -isystem/usr/include/libxml2 -isystem/System/Library/Frameworks/OpenGL.framework/Versions/Current/Headers
```