$INC{strict.pm} => PVNV

[rurban]

xs_incset uses a newSVpv_share(FILE, 0) as %INC value, which is first a proper PV, but then somehow gets turned into a PVNV without POK flag, which would explain the prereq failures in the toolchain. Easily seen with B::C, any test, for strict.pm, coretypes.pm and the 2 XSLoader.pm and DynaLoader.pm keys.

%INC is a HvSHAREKEYS, means its keys are shared in PL_strtab, and the HE is a shared_he

[rurban]

Fixed by removing the line
$INC{"strict.pm"}++ in B::C, which uncow'ed the value, and converted it to a PVNV.
See 5032167b7d80517404f4c7d03ec612dc50f61972