util: Add some additional flags for files in the m5 util.

util: Add some additional flags for files in the m5 util.

When compiling static objects, disable pie with the -no-pie linker flag.
This is necessary for x86, and doesn't seem to hurt anything for the
other variants.

When compiling shared objects, particularly the assembly files which
can't rely on the compiler to generate position independent code, define
M5OP_PIC so that the assembly code can configure itself correctly.

Change-Id: I80d1ea7a7704666027e74228036af5e0e4b9eac2
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/27218
Reviewed-by: Matthew Poremba <matthew.poremba@amd.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>