I am also getting similar issues with NDK version 19.2.*

cargo apk build          
Compiling android_native_app_glue.c
error: could not execute process 
 `/home/subhadipl/Android/Sdk/ndk-bundle/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/arm-linux-androideabi-gcc 
 /home/subhadipl/Android/Sdk/ndk-bundle/sources/android/native_app_glue/android_native_app_glue.c -c -o 
 /home/subhadipl/rusts/helloAndroid/target/android-artifacts/arm-linux-androideabi/android_native_app_glue.o --sysroot 
 /home/subhadipl/Android/Sdk/ndk-bundle/platforms/android-18/arch-arm` (never executed)

Caused by:
  No such file or directory (os error 2)

I tried "r18b" NDK and now getting a different error:

/hub/tools/android-ndk-r18b/sources/android/native_app_glue/android_native_app_glue.c:18:10: fatal error: 'jni.h' file not found

What does -c do in this command?

-c Only run preprocess, compile, and assemble steps

Looks like GCC not a part of the NDK.

android/ndk#802

How to solve it?

@shijunti19 you need to download a revision before r18b, where GCC is still present e.g.
https://developer.android.com/ndk/downloads/older_releases.html#ndk-17c-downloads

That made Compiling android_native_app_glue.c error to go away for me.

Fixed by #223.

@mb64 Could you please explain how to use master ("manual usage")? If I do what's in the readme now it still shows the same error.

The version on crates.io is an older version unfortunately. See #221. To work around, either use the docker or checkout the code from git and install using cargo install --locked --force --path . from the cargo-apk directory.