CFLAGS aren't getting set in buildtclext.tcl. Force -fPIC usage.

--- sqlite-src-3500000/tool/buildtclext.tcl.orig	2025-05-29 16:34:54.000000000 +0200
+++ sqlite-src-3500000/tool/buildtclext.tcl	2025-06-03 11:53:37.737536104 +0200
@@ -300,7 +300,7 @@
 
   # Generate and execute the command with which to do the compilation.
   #
-  set cmd "$CMD -DUSE_TCL_STUBS tclsqlite3.c -o $OUT $LIBS"
+  set cmd "$CMD -DUSE_TCL_STUBS tclsqlite3.c -fPIC -o $OUT $LIBS"
   puts $cmd
   file delete -force $OUT
   catch {exec {*}$cmd} errmsg