Move -L. to a conditional Makefile variable

Author: mhsmith

Makefile.pre.in

@@ -44,6 +44,7 @@ ABIFLAGS=	@ABIFLAGS@
 ABI_THREAD=	@ABI_THREAD@
 LDVERSION=	@LDVERSION@
 LIBPYTHON=@LIBPYTHON@
+MODULE_LDFLAGS_SHARED=$(if $(LIBPYTHON),-L. $(LIBPYTHON))
 GITVERSION=	@GITVERSION@
 GITTAG=		@GITTAG@
 GITBRANCH=	@GITBRANCH@

Modules/makesetup

@@ -277,7 +277,7 @@ sed -e 's/[ 	]*#.*//' -e '/^[ 	]*$/d' |
 				;;
 			esac
 			rule="$file: $objs \$(MODULE_${mods_upper}_LDEPS)"
-			rule="$rule; \$(BLDSHARED) $objs $libs -L. \$(LIBPYTHON) -o $file"
+			rule="$rule; \$(BLDSHARED) $objs $libs \$(MODULE_LDFLAGS_SHARED) -o $file"
 			echo "$rule" >>$rulesf
 		done
 	done

configure

@@ -6669,15 +6669,18 @@ LDVERSION='$(VERSION)$(ABIFLAGS)'
 AC_MSG_RESULT([$LDVERSION])
 
 # Configure the flags and dependencies used when compiling shared modules.
-# Do not rename LIBPYTHON - it's accessed via sysconfig by package build
-# systems (e.g. Meson) to decide whether to link extension modules against
-# libpython.
 AC_SUBST([MODULE_DEPS_SHARED])
 AC_SUBST([LIBPYTHON])
 MODULE_DEPS_SHARED='$(MODULE_DEPS_STATIC) $(EXPORTSYMS)'
+
+# On most platforms, extension modules aren't linked against libpython, so
+# LIBPYTHON must be empty.
 LIBPYTHON=''
 
 # On Android and Cygwin the shared libraries must be linked with libpython.
+# LIBPYTHON is used by python-config, python3.pc, the commands for building the
+# stdlib's own extension modules, and external package build systems via
+# sysconfig, so its value must be suitable for all those contexts.
 if test "$PY_ENABLE_SHARED" = "1" && ( test -n "$ANDROID_API_LEVEL" || test "$MACHDEP" = "cygwin"); then
   MODULE_DEPS_SHARED="$MODULE_DEPS_SHARED \$(LDLIBRARY)"
   LIBPYTHON="-lpython${VERSION}${ABIFLAGS}"