dfmc-llvm-back-end: Separate out run-time library TLV support

This change allows run-time library support for thread_local variables
to be enabled separately from use by generated Dylan code.

* sources/dfmc/llvm-back-end/llvm-targets.dylan
  (llvm-runtime-thread-local-support?): New method on <llvm-back-end>
   defining whether runtime-variable definitions should be allowed to
   use LLVM thread_local, currently always returning #t.

* sources/dfmc/llvm-back-end/llvm-primitives.dylan
  (llvm-runtime-variable): Use llvm-runtime-thread-local-support?
   rather than llvm-thread-local-support? to determine whether or not
   to use a thread-local storage model.

* sources/dfmc/llvm-back-end/llvm-back-end-library.dylan
  (module dfmc-llvm-back-end): Export llvm-runtime-thread-local-support?.

* sources/app/llvm-runtime-generator/llvm-runtime-c-header.dylan
  (print-runtime-variable-declaration): Use llvm-runtime-thread-local-support?
   rather than llvm-thread-local-support? to determine whether or not
   to declare runtime variables as __thread.

Author: housel

sources/app/llvm-runtime-generator/llvm-runtime-c-header.dylan

@@ -100,7 +100,7 @@ define method print-runtime-variable-declaration
 
   let thread-local?
     = member?(#"thread-local", descriptor.runtime-variable-attributes)
-    & llvm-thread-local-support?(be);
+    & llvm-runtime-thread-local-support?(be);
   if (thread-local?)
     format(stream, "__thread ");
   end if;

sources/dfmc/llvm-back-end/llvm-back-end-library.dylan

@@ -46,6 +46,7 @@ define module dfmc-llvm-back-end
 
     llvm-mv-struct-type,
 
+    llvm-runtime-thread-local-support?,
     llvm-thread-local-support?,
     llvm-teb-struct-type,
 

sources/dfmc/llvm-back-end/llvm-primitives.dylan

@@ -745,7 +745,7 @@ define method llvm-runtime-variable
     let attributes = descriptor.runtime-variable-attributes;
     let thread-local?
       = member?(#"thread-local", attributes)
-      & llvm-thread-local-support?(back-end);
+      & llvm-runtime-thread-local-support?(back-end);
     let section
       = llvm-section-name(back-end, descriptor.runtime-variable-section,
                           thread-local?: thread-local?);

sources/dfmc/llvm-back-end/llvm-targets.dylan

@@ -309,6 +309,12 @@ end method;
 
 /// LLVM Thread-local storage platform support
 
+define method llvm-runtime-thread-local-support?
+    (back-end :: <llvm-back-end>)
+ => (support? :: <boolean>)
+  #t
+end method;
+
 define method llvm-thread-local-support?
     (back-end :: <llvm-back-end>)
  => (support? :: <boolean>)