fsmonitor OSX: compile with DC_SHA1=YesPlease

fsmonitor OSX: compile with DC_SHA1=YesPlease

As we'll address in subsequent commits the "DC_SHA1=YesPlease" is not
on by default on OSX, instead we use Apple Common Crypto's SHA-1
implementation.

In 6beb2688d33 (fsmonitor: relocate socket file if .git directory is
remote, 2022-10-04) the build was broken with "DC_SHA1=YesPlease" (and
probably other non-"APPLE_COMMON_CRYPTO" SHA-1 backends).

So let's extract the fix for this from [1] to get the build working
again with "DC_SHA1=YesPlease". In addition to the fix in [1] we also
need to replace "SHA_DIGEST_LENGTH" with "GIT_MAX_RAWSZ".

1. https://lore.kernel.org/git/c085fc15b314abcb5e5ca6b4ee5ac54a28327cab.1665326258.git.gitgitgadget@gmail.com/

Signed-off-by: Eric DeCosta <edecosta@mathworks.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>