make.defaults: negative incrementals in USE_EXPAND (530222)

Previously, USE_EXPAND variable settings in profile make.defaults only
supported positive incremental settings. This patch adds support for
negative settings like PYTHON_TARGETS="-python3_3", which brings
behavior into alignment with PMS.

Notably, this patch does not change behavior for settings in make.conf.
In make.conf, settings to USE_EXPAND variables remain entirely
non-incremental. PMS does not govern make.conf behavior.

X-Gentoo-Bug: 530222
Acked-by: Brian Dolbec <>
(cherry picked from commit b9c06a6a2dd4ccc875f8b9dd3139ea582e1e5621)

Change-Id: Ifea1f777895742a38093e8ba25c6c81ac36bd1da
Reviewed-by: Bertrand Simonnet <>
Tested-by: Mike Frysinger <>
3 files changed