Retry compilation with gcc if -Werror is passed
Retry compilation with gcc if -Werror is passed

In some (gcc) compiler and source combinations the
compilations of the preprocessed source issues warnings
that are not shown when compiling the original source
file. This patch adds a compile retry to gcc in the same
manner as clang does if -Werror is passed.

glandium/sccache,luser/sccache2,luser/sccache2,mozilla/sccache,glandium/sccache,luser/sccache2,mozilla/sccache,luser/sccache2,mozilla/sccache,glandium/sccache,glandium/sccache