Comment # 5 on bug 937317 from Richard Biener

Not sure how -debugsource is collecting source files but the file is in

 libgcc/libgcov.c

in the source tarball.  Note that libgcov is built similar to libgcc,
one function at a time (thus libgcov.c gets compiled multiple times).
Likewise for GCC 5 where the libgcov.c file was split.

The error with gdb and the gcc5 packages is probably due to how the debug
info package creation re-writes source file paths via debugedit.

Hmm.  As libgcov.a is a static library (which is never stripped) the debuginfo
should be in the package you are building.  But of course the debugedit
machinery adjusting source paths to gcc5-debugsource (still relevant for
libgcov.a!) is _not_ applied to static libraries retaining debug information.

So this seems like a general issue with static libs and the -debugsource split.