use sha512sum to check downloads, not sha1sum

sha-1 has known collision issues, which may not be readily
exploitable yet (in our context), but we should ideally use
a more secure method for checking file integrity.

therefore, use sha-2 (sha512sum) for checking files. this is
slower than sha-1, but checksum verification is only a minor
part of what lbmk does, so the overall effect on build times
is quite negligible.

Signed-off-by: Leah Rowe <leah@libreboot.org>

script/build/release/roms

@@ -171,8 +171,8 @@ strip_archive()
 
 	(
 	cd "${romdir}" || err "strip_archive: !cd ${romdir}"
-	sha1sum *.rom >> blobhashes || \
-	    err "strip_archive: ${romdir}: !sha1sum *.rom >> blobhashes"
+	sha512sum *.rom >> blobhashes || \
+	    err "strip_archive: ${romdir}: !sha512sum *.rom >> blobhashes"
 	)
 
 	for romfile in "${romdir}"/*.rom; do