armcm_link: Fix build on recent arm gcc/newlibc versions

It seems recent arm gcc versions no longer build correctly using the
"--specs=nano.specs --specs=nosys.specs" linker flags.  Replace those
linker flags with "-nostdlib -lgcc -lc_nano".

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/generic/armcm_link.lds.S

@@ -69,5 +69,8 @@ SECTIONS
         // that isn't needed so no need to include them in the binary.
         *(.init)
         *(.fini)
+        // Don't include exception tables
+        *(.ARM.extab)
+        *(.ARM.exidx)
     }
 }