-P needed to preprocessor
Created attachment 401322 [details, diff]
patch that append -P to preprocessor part
Please work with upstream (email@example.com) regarding fixing this issue. Keeping bug open for tracking purposes on gcc porting.
They fixed it in 1.19 version. So a simple version bump is sufficient to fix the issue.
+*libgpg-error-1.19 (19 Apr 2015)
+ 19 Apr 2015; Kristian Fiskerstrand <firstname.lastname@example.org> +libgpg-error-1.19.ebuild,
+ -libgpg-error-1.15.ebuild, -libgpg-error-1.17.ebuild:
+ Version bump, fixes bug #546740. Cleanup a few old unstable versions.
This patch works for 1.13 too.