Fix path to libpython shared-library in python binaries

[yosifkit]

• prevent accidental usage of a system installed libpython of the same version

This makes the lookup for libpython dependent on where the binary is, so you can do silly things to see that it works:

$ docker run -it --rm 11314a7451b3 sh
/ # ldd /usr/local/bin/python3.11
	/lib/ld-musl-x86_64.so.1 (0x7f9295da7000)
	libpython3.11.so.1.0 => /usr/local/bin/../lib/libpython3.11.so.1.0 (0x7f92957d9000)
	libc.musl-x86_64.so.1 => /lib/ld-musl-x86_64.so.1 (0x7f9295da7000)
/ # mv /usr/local/ /opt/things/
/ # ldd /opt/things/bin/python3.11
	/lib/ld-musl-x86_64.so.1 (0x7f388530a000)
	libpython3.11.so.1.0 => /opt/things/bin/../lib/libpython3.11.so.1.0 (0x7f3884d3c000)
	libc.musl-x86_64.so.1 => /lib/ld-musl-x86_64.so.1 (0x7f388530a000)
/ # 

Fixes #784

[yosifkit]

• \$ because of the double quotes in the shell to prevent interpolation
• $$ for make to not interpret the $O
• " because it needed the ' around the path, but I didn't want ='-Wl,-rpath='"'"'$$ORIGIN/../lib'"'"

[tianon]

Suggested change

	LDFLAGS="-Wl,--strip-all,-rpath='$\$ORIGIN/../lib'" \
	# \$ because of the double quotes in the shell to prevent interpolation
	# $$ for make to not interpret the $O
	# " because it needed the ' around the path, but I didn't want ='-Wl,-rpath='"'"'$$ORIGIN/../lib'"'"
	LDFLAGS="-Wl,-rpath='\$\$ORIGIN/../lib'{{ if is_slim or is_alpine then ",--strip-all" else "" end }}" \

(and then dropping the outer if? 👀)