build-busybox: Disable building the AR applet

When building with mingw32-make, it prefers executing commands
through "sh.exe" if it is available.

When busybox sh.exe executes "ar", it prefers executing its own
internal tool over a potential external tool found in $PATH.

(This can be avoided by setting 'export BB_OVERRIDE_APPLETS="ar"',
but as this build of busybox is expected to be used with llvm-mingw,
disable the built-in "ar" tool outright.)

build-busybox.sh

@@ -72,6 +72,7 @@ fi
 mkdir -p $BUILDDIR
 make mingw64a_defconfig O=$BUILDDIR -j$CORES
 cd $BUILDDIR
+sed -ri 's/^(CONFIG_AR)=y/\1=n/' .config
 $MAKE -j$CORES CROSS_COMPILE=${HOST+$HOST-}
 cp ../LICENSE $PREFIX/LICENSE.txt
 mkdir -p $PREFIX/bin