configure: Explicitly disable PIC when targeting win32/mingw

These platforms do not have any notion of PIC. On some compilers,
enabling pic produces a number of warnings.

This avoids trying to produce PIC loads in the ARM assembly - there
are no relocation types in PE/COFF that correspond to
BFD_RELOC_32_PCREL (R_ARM_REL32 in ELF).

As a side-effect, this avoids enabling PIC on mingw64, getting rid
of the warnings about PIC not having any effect on that platform.
Signed-off-by: Martin Storsjö <martin@martin.st>

configure

@@ -3044,6 +3044,7 @@ case $target_os in
         dlltool="${cross_prefix}dlltool"
         ranlib=:
         enable dos_paths
+        disable pic
         ;;
     win32|win64)
         if enabled shared; then
@@ -3068,6 +3069,7 @@ case $target_os in
         objformat="win32"
         ranlib=:
         enable dos_paths
+        disable pic
         ;;
     cygwin*)
         target_os=cygwin