configure: Don't explicitly disable PIC for windows targets

This reverts e08c946c6 and 05165c2f7a. The actual intention of
e08c946c6 was to fix shared library builds for arm/win32, which
can also be accomplished in other ways.

Disabling pic on those platforms broke inline assembly on cygwin/64
(since some inline assembly requires knowing whether we are building
as PIC or not), and might also break inline assembly on other
compilers on windows.

As a side-effect, this unfortunately brings back all the warnings
about PIC not having any effect on that platform.

Signed-off-by: Martin Storsjö <martin@martin.st>

configure

@@ -3124,7 +3124,6 @@ case $target_os in
         dlltool="${cross_prefix}dlltool"
         ranlib=:
         enable dos_paths
-        disable pic
         ;;
     win32|win64)
         if enabled shared; then
@@ -3149,7 +3148,6 @@ case $target_os in
         objformat="win32"
         ranlib=:
         enable dos_paths
-        disable pic
         ;;
     cygwin*)
         target_os=cygwin
@@ -3164,7 +3162,6 @@ case $target_os in
         SHFLAGS='-shared -Wl,--out-implib,$(SUBDIR)lib$(FULLNAME).dll.a'
         objformat="win32"
         enable dos_paths
-        disable pic
         ;;
     *-dos|freedos|opendos)
         network_extralibs="-lsocket"