Avoid DYLD_LIBRARY_PATH for in-tree tclsh

vendor/Makefile.in

@@ -64,6 +64,9 @@ destroot: $(DESTROOT_TARGETS)
 destroot-tcl: all-tcl
 	@echo ===\> staging to destroot in ${DIRPRFX}@VENDOR_TCL_SUBDIR@
 	@umask 0022; $(MAKE) -C @VENDOR_TCL_SUBDIR@ "DESTDIR=${DESTROOT}" @VENDOR_TCL_INSTALL@
+	[ "@OS_PLATFORM@" != darwin ] || install_name_tool -change "$(MP_PREFIX)/lib/libtcl@TCL_VERSION@.dylib" \
+	    "@executable_path/../lib/libtcl@TCL_VERSION@.dylib" \
+	    "$(DESTROOT)$(MP_PREFIX)/bin/tclsh@TCL_VERSION@"
 
 destroot-tclx: all-tclx
 	@echo ===\> staging to destroot in ${DIRPRFX}@VENDOR_TCLX_SUBDIR@

vendor/tclsh.in

@@ -4,19 +4,15 @@ DESTROOT="@abs_top_builddir@/vendor/vendor-destroot"
 MP_PREFIX="@prefix@/libexec/macports"
 LIB_PATH="${DESTROOT}${MP_PREFIX}/lib:${DESTROOT}${MP_PREFIX}/lib/@SQLITE3_LIBNAME@"
 
-# For macOS
-if [ -z "$DYLD_LIBRARY_PATH" ]; then
-    export DYLD_LIBRARY_PATH="$LIB_PATH"
-else
-    export DYLD_LIBRARY_PATH="$LIB_PATH:$DYLD_LIBRARY_PATH"
-fi
-
 # For Linux and *BSD
 if [ -z "$LD_LIBRARY_PATH" ]; then
     export LD_LIBRARY_PATH="$LIB_PATH"
 else
     export LD_LIBRARY_PATH="$LIB_PATH:$LD_LIBRARY_PATH"
 fi
+# DYLD_LIBRARY_PATH tends to get lost on recent macOS due to basic
+# tools like /bin/sh being subject to SIP, so we have to edit the load
+# commands instead (see vendor/Makefile.in).
 
 export TCLLIBPATH="${DESTROOT}${MP_PREFIX}/lib"