Installing on ARM M1 Macs

Apologies if this isn't the right place since I think it might just be an issue with postgres app issue.

I'm trying to install pg_cron on a macbook with the M1 chip. I'm getting the following error when trying to run the makefile:

```
gcc -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Werror=vla -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -Wno-unused-command-line-argument -Os -mmacosx-version-min=10.12 -bundle -multiply_defined suppress -o pg_cron.so src/entry.o src/job_metadata.o src/misc.o src/pg_cron.o src/task_states.o -L/Applications/Postgres.app/Contents/Versions/12/lib -L/Applications/Postgres.app/Contents/Versions/12/lib -L/Applications/Postgres.app/Contents/Versions/12/lib -Wl,-dead_strip_dylibs -L/Applications/Postgres.app/Contents/Versions/12/lib -lpq -bundle_loader /Applications/Postgres.app/Contents/Versions/12/bin/postgres
ld: warning: ignoring file /Applications/Postgres.app/Contents/Versions/12/lib/libpq.dylib, building for macOS-arm64 but attempting to link with file built for macOS-x86_64
ld: can't link with a main executable file '/Applications/Postgres.app/Contents/Versions/12/bin/postgres' for architecture arm64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [pg_cron.so] Error 1
```

I'm using the postgres app for mac and pg_config seems alright. Has anyone else had this issue before?

_Update, it seems to work if postgres is installed through homebrew instead of the postgres app_
_Update 2: I couldn't use the homebrew installation for other reasons, I fixed it by compiling pg_cron on an intel mac and running make install on the M1 mac_

Start with the Makefile and the pg_config output for the Postgres.app installation; reproduce the link step on an ARM M1 Mac and compare it with the Homebrew setup. Done means pg_cron builds and installs against an arm64 PostgreSQL installation without linking x86_64 libraries or the postgres executable.

Written by the indexing model from the issue text.