maintainer-feedback requested: [Bug 263353] lang/python38: fix excessive ld.lld memory use with LTO in port options

Bugzilla Automation <bugzilla@FreeBSD.org> has asked freebsd-python (Nobody)
<python@FreeBSD.org> for maintainer-feedback:
Bug 263353: lang/python38: fix excessive ld.lld memory use with LTO in port
options
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=263353



--- Description ---
I can no longer build Python 3.8 on a FreeBSD 13.0-RELEASE amd64 computer with
1.6 GB available memory (1 GB physical, 1 GB encrypted swap file on UFS).

The upstream configure.ac file in Python 3.8.13 as of 0058eede0ebf adds "-flto
-g" to the build (through CFLAGS and LDFLAGS). This happens even without
WITH_DEBUG=yes.

This considerably increases the memory that my FreeBSD 13.0-RELEASE ld.lld
requires, and the kernel kills it with "out of swap space". 

I used to be able to build Python 3.8 on that machine earlier, and reviewing
port history, I surmise that * 9a31e1b6d3bf 2022-03-09 | lang/python3*: add LTO
option and enable by default everywhere except powerpc64 and riscv64 [Piotr
Kubaj] 
caused the increase in memory consumption from the desired LTO.

Chopping out the -g from CFLAGS and LDFLAGS fixes this for me, reducing linker
memory consumption to below 400 MB VMEM, and lets my low-on-RAM computer
complete the build. (It is a single Xeon core I rented out for a virtual
server.)

I am proposing the attached patch. I have not investigated yet whether Pythons
3.7 3.9 3.10 3.11 need an analogue patch, for lack of time. In Python 3.8 you
will see "-flto -g" in the ${WRKSRC}/Makefile that results from a "make
configure" with LTO option enabled, because the upstream configure.ac is
written that way.