ld: adjust PE base relocations testcase

mcore-pe and sh-pe pointed out that the testcase added by 6fa7408d
("ld: don't generate base relocations in PE output for absolute
symbols") wasn't quite generic enough yet. Copy entry point stuff from
another test and increase alignment to also cover targets with a page
size lower than 4k.

Despite all of this the test needs to be xfail-ed for mcore, as this
target isn't included in the set getting DLL_SUPPORT enabled in
emultempl/pe.em, and hence no base relocations get generated there
(yet).