I am building a C app for android, I use 'sigemptyset' in my app, when I compile the code using NDK it is compiled successfully, but when running the app I get
cannot locate symbol 'sigemptyset'
TARGET_PLATFORM := android-19
The cause of problem is not the version of NDK that was used but version of target platform.
android-19 is the last platform version where
sigemptyset() (and many other functions) was declared as inline just at platform headers. As result - system libc on that devices doesn't contain such functions. So you are right - you should use proper target platform to allow your code to run on older devices. But you are doing it incorrectly. All that you need is add
APP_PLATFORM := android-19