Add NDK version to tags

[psyhtest]

I have several NDKs installed:

android-ndk-r13b/ android-ndk-r17b/ android-ndk-r18b/

and some compilers detected:

anton@velociti:~$ ck show env --tags=compiler,android
Env UID:         Target OS:      Bits: Name:                     Version: Tags:

1c70f43a4910bf0c android28-arm64    64 Android NDK LLVM compiler 7.0.2    64bits,android,compiler,host-os-linux-64,lang-c,lang-cpp,llvm,ndk,target-os-android28-arm64,v7,v7.0,v7.0.2
fbe5a0899e47cda8 android28-arm64    64 Android NDK GCC compiler  clang    64bits,android,compiler,gcc,host-os-linux-64,lang-c,lang-cpp,ndk,target-os-android28-arm64,v0
f58acb20767b3ac2 android24-arm64    64 Android NDK LLVM compiler 6.0.2    64bits,android,compiler,host-os-linux-64,lang-c,lang-cpp,llvm,ndk,target-os-android24-arm64,v6,v6.0,v6.0.2
9a7394e1429c8ed0 android24-arm64    64 Android NDK GCC compiler  4.9.x    64bits,android,compiler,gcc,host-os-linux-64,lang-c,lang-cpp,ndk,target-os-android24-arm64,v4,v4.9,v4.9.0

It's not easy, however, to see which NDKs the compilers come from:

$ ck cat env --tags=compiler,android | grep CK_ENV_COMPILER.*BIN | grep -v PATH
export CK_ENV_COMPILER_GCC_BIN=/home/anton/data/android-ndk-r17b/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin
export CK_ENV_COMPILER_LLVM_BIN=/home/anton/data/android-ndk-r17b/toolchains/llvm/prebuilt/linux-x86_64/bin
export CK_ENV_COMPILER_GCC_BIN=/home/anton/data/android-ndk-r18b/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin
export CK_ENV_COMPILER_LLVM_BIN=/home/anton/data/android-ndk-r18b/toolchains/llvm/prebuilt/linux-x86_64/bin

I guess that LLVM 6.0.2 and GCC 4.9.x are in NDK r17b, while LLVM 7.0.2 (and a weird GCC clang) is in NDK r18b, but it would be better to include the NDK version in the tags.