PHash fatal error: 'sys/sysctl.h' file not found

Question

I am trying to add c++ native project to my library project.

I have followed this tutorial

and I get fatal error: 'sys/sysctl.h' file not found can't figure out why.

I have followed this steps:
1) create a JNI Folder and put there all the source files and the wrapper.
2) created CMakeLIsts.txt

This is my CMakeLIsts.txt :

cmake_minimum_required(VERSION 3.4.1)

add_library(pHash-jni SHARED
            pHash-jni.cpp)


target_link_libraries(pHash-jni log android)

3) updated my local.propreties to this :

    ndk.dir=/home/maxim/Android/Sdk/ndk-bundle
    sdk.dir=/home/maxim/Android/Sdk

4) updated build.gradle to this :

apply plugin: 'com.android.library'

android {
    compileSdkVersion 24
    buildToolsVersion "24.0.2"

    defaultConfig {
        minSdkVersion 15
        targetSdkVersion 24
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                arguments '-DANDROID_TOOLCHAIN=clang'
                cppFlags "-fexceptions"

            }
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    externalNativeBuild {
        cmake {
            path "src/main/jni/CMakeLists.txt"
        }
    }
    productFlavors {
        arm7 {
            // in the future, ndk.abiFilter might also work
            ndk {
                abiFilter 'armeabi-v7a'
            }
        }
        arm8 {
            ndk {
                abiFilters 'arm64-v8a'
            }
        }
        arm {
            ndk {
                abiFilter 'armeabi'
            }
        }
        x86 {
            ndk {
                abiFilter 'x86'
            }
        }
        x86_64 {
            ndk {
                abiFilter 'x86_64'
            }
        }
        mips {
            ndk {
                abiFilters 'mips', 'mips64'
            }
        }
        all {
            ndk {
                abiFilters 'mips', 'mips64', 'x86', 'x86_64'
            }
        }
    }
    sourceSets { main { jni.srcDirs = ['src/main/jni', 'src/main/jni/'] } }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:24.2.1'
    testCompile 'junit:junit:4.12'
}

5) updated gradle.properties to with this :

android.useDeprecatedNdk=true

Answer 1

$ find android-ndk-r13/platforms/ -name sysctl.h                                                                                                             
../../android-ndk-r13/platforms/android-19/arch-arm/usr/include/linux/sysctl.h
more of the same...

Android doesn't have <sys/sysctl.h>, but it does have <linux/sysctl.h>.