rts: Fix m32 allocator build on Windows

An inconsistency in the name of m32_allocator_flush caused the build to
fail with a missing prototype error.

rts/linker/M32Alloc.c

@@ -454,24 +454,26 @@ m32_alloc(struct m32_allocator_t *alloc, size_t size, size_t alignment)
 // See the note titled "Compile Time Trickery" at the top of this file.
 
 m32_allocator *
-m32_allocator_new(bool executable)
+m32_allocator_new(bool executable STG_UNUSED)
 {
     barf("%s: RTS_LINKER_USE_MMAP is %d", __func__, RTS_LINKER_USE_MMAP);
 }
 
-void m32_allocator_free(m32_allocator *alloc)
+void m32_allocator_free(m32_allocator *alloc STG_UNUSED)
 {
     barf("%s: RTS_LINKER_USE_MMAP is %d", __func__, RTS_LINKER_USE_MMAP);
 }
 
 void
-m32_flush(void)
+m32_allocator_flush(m32_allocator *alloc STG_UNUSED)
 {
     barf("%s: RTS_LINKER_USE_MMAP is %d", __func__, RTS_LINKER_USE_MMAP);
 }
 
 void *
-m32_alloc(size_t size STG_UNUSED, size_t alignment STG_UNUSED)
+m32_alloc(m32_allocator *alloc STG_UNUSED,
+          size_t size STG_UNUSED,
+          size_t alignment STG_UNUSED)
 {
     barf("%s: RTS_LINKER_USE_MMAP is %d", __func__, RTS_LINKER_USE_MMAP);
 }

rts/linker/M32Alloc.h

@@ -8,7 +8,7 @@
 
 #pragma once
 
-#if RTS_LINKER_USE_MMAP
+#if RTS_LINKER_USE_MMAP == 1
 #include <fcntl.h>
 #include <sys/mman.h>
 

rts/linker/PEi386.c

@@ -1826,6 +1826,8 @@ makeSymbolExtra_PEi386( ObjectCode* oc, uint64_t index, size_t s, char* symbol )
     return (size_t)extra->jumpIsland;
 }
 
+void ocProtectExtras(ObjectCode* oc STG_UNUSED) { }
+
 #endif /* x86_64_HOST_ARCH */
 
 bool