gh-115028: Add support for relocatable installations using $ORIGIN in RPATH

This patch adds a new configure option --with-relative-rpath that, when
enabled, adds $ORIGIN-based RPATHs to binaries when building Python on Linux.
This makes Python installations relocatable so they can be moved to different
directories without breaking dynamic library dependencies.

Three new variables are introduced to set RPATHs for different components:
- PY_RPATH_EXEC: For the Python interpreter binary
- PY_RPATH_LIB: For the shared libpython library
- PY_RPATH_MOD: For Python extension modules

This is a step toward solving the relocatability issues discussed in
packaging forums and helps ena

Author: pablogsal

Makefile.pre.in

@@ -1,4 +1,4 @@
-# Top-level Makefile for Python
+# Top-level Makeile for Python
 #
 # As distributed, this file is called Makefile.pre.in; it is processed
 # into the real Makefile by running the script ./configure, which
@@ -58,6 +58,9 @@ DTRACE_HEADERS= @DTRACE_HEADERS@
 DTRACE_OBJS=    @DTRACE_OBJS@
 DSYMUTIL=       @DSYMUTIL@
 DSYMUTIL_PATH=  @DSYMUTIL_PATH@
+PY_RPATH_EXEC=  @PY_RPATH_EXEC@
+PY_RPATH_LIB=   @PY_RPATH_LIB@
+PY_RPATH_MOD=   @PY_RPATH_MOD@
 
 GNULD=		@GNULD@
 
@@ -915,7 +918,8 @@ clinic-tests: check-clean-src $(srcdir)/Lib/test/clinic.test.c
 
 # Build the interpreter
 $(BUILDPYTHON):	Programs/python.o $(LINK_PYTHON_DEPS)
-	$(LINKCC) $(PY_CORE_LDFLAGS) $(LINKFORSHARED) -o $@ Programs/python.o $(LINK_PYTHON_OBJS) $(LIBS) $(MODLIBS) $(SYSLIBS)
+	$(LINKCC) $(PY_CORE_LDFLAGS) $(LINKFORSHARED) $(PY_RPATH_EXEC) -o $@ Programs/python.o $(LINK_PYTHON_OBJS) $(LIBS) $(MODLIBS) $(SYSLIBS)
+
 
 platform: $(PYTHON_FOR_BUILD_DEPS) pybuilddir.txt
 	$(RUNSHARED) $(PYTHON_FOR_BUILD) -c 'import sys ; from sysconfig import get_platform ; print("%s-%d.%d" % (get_platform(), *sys.version_info[:2]))' >platform
@@ -945,7 +949,7 @@ $(LIBRARY): $(LIBRARY_OBJS)
 	$(AR) $(ARFLAGS) $@ $(LIBRARY_OBJS)
 
 libpython$(LDVERSION).so: $(LIBRARY_OBJS) $(DTRACE_OBJS)
-	$(BLDSHARED) -Wl,-h$(INSTSONAME) -o $(INSTSONAME) $(LIBRARY_OBJS) $(MODLIBS) $(SHLIBS) $(LIBC) $(LIBM)
+	$(BLDSHARED) -Wl,-h$(INSTSONAME) $(PY_RPATH_LIB) -o $(INSTSONAME) $(LIBRARY_OBJS) $(MODLIBS) $(SHLIBS) $(LIBC) $(LIBM)
 	if test $(INSTSONAME) != $@; then \
 		$(LN) -f $(INSTSONAME) $@; \
 	fi

Modules/makesetup

@@ -274,7 +274,7 @@ sed -e 's/[ 	]*#.*//' -e '/^[ 	]*$/d' |
 				;;
 			esac
 			rule="$file: $objs"
-			rule="$rule; \$(BLDSHARED) $objs $libs \$(LIBPYTHON) -o $file"
+			rule="$rule; \$(BLDSHARED) \$(PY_RPATH_MOD) $objs $libs \$(LIBPYTHON) -o $file"
 			echo "$rule" >>$rulesf
 		done
 	done

configure

@@ -3356,6 +3356,38 @@ AC_MSG_RESULT([no])
 with_tsan="no"
 ])
 
+# Check for --with-relative-rpath
+AC_MSG_CHECKING([for --with-relative-rpath])
+AC_ARG_WITH([relative-rpath],
+  [AS_HELP_STRING([--with-relative-rpath],
+    [use relative rpath with $ORIGIN for binaries (Linux only)])],
+  [], [with_relative_rpath=no])
+
+# Initialize empty RPATH variables
+PY_RPATH_EXEC=""
+PY_RPATH_LIB=""
+PY_RPATH_MOD=""
+
+if test "$with_relative_rpath" = "yes"; then
+  if test "$ac_sys_system" = "Linux"; then
+    # Define the RPATH settings for each binary type
+    PY_RPATH_EXEC="-Wl,-rpath,\\\$\$ORIGIN/../\$(PLATLIBDIR)"
+    PY_RPATH_LIB="-Wl,-rpath,\\\$\$ORIGIN"
+    PY_RPATH_MOD="-Wl,-rpath,\\\$\$ORIGIN/../../"
+    AC_MSG_RESULT([yes])
+  else
+    AC_MSG_RESULT([no - only supported on Linux])
+    with_relative_rpath=no
+  fi
+else
+  AC_MSG_RESULT([no])
+fi
+
+# Export these variables for the Makefile
+AC_SUBST([PY_RPATH_EXEC])
+AC_SUBST([PY_RPATH_LIB])
+AC_SUBST([PY_RPATH_MOD])
+
 # Set info about shared libraries.
 AC_SUBST([SHLIB_SUFFIX])
 AC_SUBST([LDSHARED])