Introduce compiler wrappers

For a long time orchestra has been struggling to make sure each
component was getting the C/C++ flags we wanted. Each build systems do
that differently. Morover, since we have certain "contradictory" options
for compile- and link-time, we have been having issues with build
systems building and linking in a single shot.

This commit radically solves this issue by introducing
`hard-flags-compiler-wrapper.py`, a wrapper script for compilers that:

1. Splits linking and compilation inspecting the command line.

2. Detects from environment variables which additional flags to
   pass. Depending on the name of the environment variable, the flag can
   be used only for a certain compiler (e.g., `clang`), only for a
   certain language (e.g., `cxx`) or only for a certain action (e.g.,
   "compile" vs "link").

This provides us the maximum flexibility and, since this new method is
"embedded" in the compiler, bypasses all the build systems
specific-issues.

Also, it significantly makes the description much more readable and
compact.