Bump Android API level to 23 to allow it to run on Android 10

Nobody cares about older API versions, which would only be needed
to support Android versions older than 6.0.

cf. https://gitlab.com/openconnect/openconnect/-/merge_requests/92

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

android/Makefile

@@ -10,15 +10,18 @@
 #
 # It should also be fairly simple to extend this to cross-compile for any target
 
-NDK     := /opt/android-sdk-linux_x86/android-ndk-r16b
-ARCH    := arm
+# Last tested with https://dl.google.com/android/repository/android-ndk-r21b-linux-x86_64.zip
+
+
+NDK     := /opt/android-sdk-linux_x86/android-ndk-r21b
+ARCH    := x86_64
+API_LEVEL := 23
 
 EXTRA_CFLAGS :=
 
 # You should be able to just 'make ARCH=x86' and it should DTRT.
 ifeq ($(ARCH),arm)
 TRIPLET := arm-linux-androideabi
-API_LEVEL := 14
 EXTRA_CFLAGS := -march=armv7-a -mthumb
 endif
 ifeq ($(ARCH),arm64)
@@ -27,11 +30,9 @@ API_LEVEL := 26
 endif
 ifeq ($(ARCH),x86)
 TRIPLET := i686-linux-android
-API_LEVEL := 14
 endif
 ifeq ($(ARCH),x86_64)
 TRIPLET := x86_64-linux-android
-API_LEVEL := 21
 endif
 
 TOPDIR := $(shell pwd)