Perform the environment modifications specific to DISTUTILS_EXT
to python_compile and python_test phases. These are the only phases
where we expect extension builds to be called. This allows us to
limit the scope of localized CPPFLAGS, as we both want to avoid leaking
changes to non-Python parts of the build and let ebuilds to manipulate
flags at their leisure, particularly prior to python_compile.

Signed-off-by: Michał Górny <mgorny@gentoo.org>
---
eclass/distutils-r1.eclass | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/eclass/distutils-r1.eclass b/eclass/distutils-r1.eclass
index fb0c2dfaa693..60554944a5a0 100644
--- a/eclass/distutils-r1.eclass
+++ b/eclass/distutils-r1.eclass
@@ -1812,7 +1812,13 @@ distutils-r1_run_phase() {
local -x AR=${AR} CC=${CC} CPP=${CPP} CXX=${CXX}
tc-export AR CC CPP CXX

- if [[ ${DISTUTILS_EXT} ]]; then
+ # Perform additional environment modifications only for python_compile + # phase. This is the only phase where we expect to be calling the Python
+ # build system. We want to localize the altered variables to avoid them
+ # leaking to other parts of multi-language ebuilds. However, we want
+ # to avoid localizing them in other phases, particularly
+ # python_configure_all, where the ebuild may wish to alter them globally.
+ if [[ ${DISTUTILS_EXT} && ( ${1} == *compile* || ${1} == *test* ) ]]; then
local -x CPPFLAGS="${CPPFLAGS} $(usex debug '-UNDEBUG' '-DNDEB