setup: fix installing in a mingw environment
The addition, in
9a4adc76c88a, of a hack for the MSVC compiler class was
overwriting the original class for the Mingw32CCompiler class, leading to an
error when the HackedMingw32CCompiler is instantiated.
Differential Revision: https://phab.mercurial-scm.org/D329
$ hg init
$ touch unknown
$ touch a
$ hg add a
$ hg ci -m "1"
$ touch b
$ hg add b
$ hg ci -m "2"
Should show unknown
$ hg status
? unknown
$ hg revert -r 0 --all
removing b
Should show unknown and b removed
$ hg status
R b
? unknown
Should show a and unknown
$ ls
a
unknown