libnspr: remove thumb2 handling

libnspr: remove thumb2 handling

libnspr currently passes --enable-thumb2 if the CPU has thumb
instructions. This option will pass -mthumb to the compiler. However,
if an external multilib toolchain is used that has a thumb-specific
variant (e.g. Sourcery), it will try to use that one. But we only copy
a single variant to the sysroot, so the build will fail with:

.../arm-none-linux-gnueabi/bin/ld: cannot find crti.o: No such file or directory
...
collect2: error: ld returned 1 exit status
../../config/rules.mk:303: recipe for target 'libnspr4.so' failed

We can in fact just remove the thumb2 handling. With current libnspr,
the thumb and thumb2 options just add -marm and -mthumb. But we already
pass that in our toolchain wrapper so it's completely redundant.

Note that when nothing is passed, the configure script still tries to
autodetect whether thumb2 is available (but doesn't do it correctly,
see the error above), but in the end it doesn't use the result for
anything. In other words, even if it detects that thumb2 is available,
it will _not_ pass -mthumb to the compiler.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>