Use system build variables when building liblua52.so (#517)

Related to #515, liblua52.so can be built using the system CFLAGS
variable. I noticed when building/modifying the AUR package that running
the build script only included `-fPIC`, and built using only `-O2 -Wall
-DLUA_COMPAT_ALL -DLUA_USE_LINUX -fPIC`. This didn't compile using the
debug options set by makepkg.

Adding `${CFLAGS}` to MYCFLAGS in the build script allowed the library
to compile with those symbols, as well as other security mitigations.
SYSCFLAGS is set explicitly in Lua's Makefile, so it's safer to change
MYCFLAGS and MYLDFLAGS instead without patching.

Author: shpaass

changelog.txt

@@ -31,6 +31,7 @@ Date:
         - Don't draw table intermediates as <1μ ingredients/products.
     Internal changes:
         - Enable mod-fixes for the data, data-updates, and data-final-fixes files.
+        - Recompile the lua lib for linux (PR 515). The script now uses CFLAGS and LDFLAGS.
 ----------------------------------------------------------------------------------------------------------------------
 Version: 2.14.0
 Date: June 15th 2025

lua/README.md

@@ -1,6 +1,7 @@
 # Compiling liblua52.so
 
-Simply run `./build-linux.sh` to (re)build liblua52.so and copy it over to Yafc.
+Simply run `./build-linux.sh` to (re)build liblua52.so and copy it over to Yafc. The script will compile 
+lua with your CFLAGS and LDFLAGS, so feel free to use them if you need debug symbols or security tweaks, for instance.
 
 It will take the following steps
 1. Download the source, if not available (from https://www.lua.org/ftp/)

lua/build-linux.sh

@@ -28,7 +28,7 @@ patch -p0 -i "liblua.so.patch" || exit 1
 patch -d "lua-5.2.1/src" -p1 -i "../../lua-5.2.1.patch" || exit 1
 
 echo "Compiling Lua 5.2.1"
-make -C "lua-5.2.1" linux MYCFLAGS="-fPIC"
+make -C "lua-5.2.1" linux MYCFLAGS="-fPIC ${CFLAGS}" MYLDFLAGS="${LDFLAGS}"
 
 echo "Copying liblua.so to Yafc"
 cp "lua-5.2.1/src/liblua.so.5.2.1"  ../Yafc/lib/linux/liblua52.so