Why do 'x86' and 'armeabi-v7a' abis set NDK platform level to 19 when other archs set it to 21

[bitmold]

Whereas x86_64 and arm64-v8a set the NDK level to 21.

I assume that this is a mistake/bug. Starting in NDK 26 the min SDK is 21 anyway, and NDK 25 was end of life'd already: android/ndk#1751

Orbot I think targets 21+ too fwiw.

ifneq ($(filter arm64-v8a, $(APP_ABI)),)
 HOST := aarch64-linux-android
 ALTHOST := $(HOST)
 GREP_CHECK := aarch64
 NDK_ABI := arm64
 NDK_BIT := 64
 NDK_PLATFORM_LEVEL := 21
 NDK_TOOLCHAIN := $(HOST)-$(NDK_TOOLCHAIN_VERSION)
endif
ifneq ($(filter armeabi-v7a, $(APP_ABI)),)
 HOST := armv7a-linux-androideabi
 ALTHOST := arm-linux-androideabi
 GREP_CHECK := EABI5
 NDK_ABI := arm
 NDK_BIT := 32
 NDK_PLATFORM_LEVEL := 19
 NDK_TOOLCHAIN := $(HOST)-$(NDK_TOOLCHAIN_VERSION)
endif
ifneq ($(filter x86, $(APP_ABI)),)
 HOST := i686-linux-android
 ALTHOST := $(HOST)
 GREP_CHECK := 80386
 NDK_ABI := x86
 NDK_BIT := 32
 NDK_PLATFORM_LEVEL := 19
 NDK_TOOLCHAIN := $(NDK_ABI)-$(NDK_TOOLCHAIN_VERSION)
endif
ifneq ($(filter x86_64, $(APP_ABI)),)
 HOST := x86_64-linux-android
 ALTHOST := $(HOST)
 GREP_CHECK := x86-64
 NDK_ABI := x86_64
 NDK_BIT := 64
 NDK_PLATFORM_LEVEL := 21
 NDK_TOOLCHAIN := $(NDK_ABI)-$(NDK_TOOLCHAIN_VERSION)
endif

Dropping Support for <= 20 decreases library size too.

cc @eighthave @n8fr8

[syphyr]

I have been trying to get NDK 26 to work, but it has issues with including the jni parts of the code added to tor from the following commit:
guardianproject/tor@63d4d99

tor-anroid will appear to build sucessfully with NDK 26, but these jni additions from the commit above will be stripped out of libtor.so and orbot will then segfault on startup.