elf: Add a test for PT_LOAD segments with p_align == 1 [BZ #28688]

Add tst-p_alignmod2-edit to edit the copy of tst-p_alignmod-base.so to
set p_align of the first PT_LOAD segment to 1 and verify that the shared
library can be loaded normally.

Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>