In Android Studio, gradle creates directory .externalNativeBuild under the module root, for each module that has NDK integration, via CMake or ndk-build.

For CMake, the gradle plugin is quite verbose. For each build variant it creates separate subdirectory, e.g. .externalNativeBuild/cmake/debug/x86 or .externalNativeBuild/cmake/release/armeabi-v7a, etc.

Each directory contains some useful files: cmake_build_command.txt describes the actual parameters passed to CMake; android_gradle_build.json shows what parameters the gradle plugin derived for your binaries; from build.ninja you can deduce the how these parameters were applied for each compilation or linkage step.

For ndk-build, the android_gradle_build.json file is also quite useful. ndkBuild_build_command.txt lists all parameters passed to ndk-build command, and ndkBuild_build_output.txt is the unabridged output of that command. You can easily add V=1 to the arguments, e.g.

externalNativeBuild {

  ndkBuild {

    cppFlags "-std=c++11"

    arguments "APP_STL=c++_static", "APP_OPTIM=release", "NDK_DEBUG=0", "V=1"

    abiFilters "armeabi-v7a"

  }

}

For CMake, the relevant argument is "-DCMAKE_VERBOSE_MAKEFILE:BOOL=ON" (see explanation and alternatives):

externalNativeBuild {

  cmake {

    cppFlags "-std=c++11"

    arguments "-DCMAKE_VERBOSE_MAKEFILE:BOOL=ON"

    abiFilters "armeabi-v7a"

  }

}

Without CMAKE_VERBOSE_MAKEFILE, the Gradle Console displays:

:app:externalNativeBuildDebug

Build native-lib armeabi-v7a

[1/2] Building CXX object CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o

[2/2] Linking CXX shared library ../../../../build/intermediates/cmake/debug/obj/armeabi-v7a/libnative-lib.so

With "-DCMAKE_VERBOSE_MAKEFILE:BOOL=ON", I get tons of output:

:app:externalNativeBuildDebug

Build native-lib armeabi-v7a

[1/2] /Users/alex/Library/Android/sdk/ndk-bundle/toolchains/llvm/prebuilt/darwin-x86_64/bin/clang++  --target=armv5te-none-linux-androideabi --gcc-toolchain=/Users/alex/Library/Android/sdk/ndk-bundle/toolchains/arm-linux-androideabi-4.9/prebuilt/darwin-x86_64 --sysroot=/Users/alex/Library/Android/sdk/ndk-bundle/platforms/android-14/arch-arm  -Dnative_lib_EXPORTS -isystem /Users/alex/Library/Android/sdk/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/include -isystem /Users/alex/Library/Android/sdk/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/libs/armeabi-v7a/include -isystem /Users/alex/Library/Android/sdk/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/include/backward -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -march=armv5te -mtune=xscale -msoft-float -fno-integrated-as -mthumb -Wa,--noexecstack -Wformat -Werror=format-security  -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -march=armv5te -mtune=xscale -msoft-float -fno-integrated-as -mthumb -Wa,--noexecstack -Wformat -Werror=format-security   -O0 -fno-limit-debug-info -O0 -fno-limit-debug-info  -fPIC -MD -MT CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o -MF CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o.d -o CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o -c /Users/alex/test/egl/app/src/main/cpp/native-lib.cpp

[2/2] : && /Users/alex/Library/Android/sdk/ndk-bundle/toolchains/llvm/prebuilt/darwin-x86_64/bin/clang++  --target=armv5te-none-linux-androideabi --gcc-toolchain=/Users/alex/Library/Android/sdk/ndk-bundle/toolchains/arm-linux-androideabi-4.9/prebuilt/darwin-x86_64 --sysroot=/Users/alex/Library/Android/sdk/ndk-bundle/platforms/android-14/arch-arm -fPIC -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -march=armv5te -mtune=xscale -msoft-float -fno-integrated-as -mthumb -Wa,--noexecstack -Wformat -Werror=format-security  -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -march=armv5te -mtune=xscale -msoft-float -fno-integrated-as -mthumb -Wa,--noexecstack -Wformat -Werror=format-security   -O0 -fno-limit-debug-info -O0 -fno-limit-debug-info  -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -Wl,--no-undefined -Wl,-z,noexecstack -Qunused-arguments -Wl,-z,relro -Wl,-z,now -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -Wl,--no-undefined -Wl,-z,noexecstack -Qunused-arguments -Wl,-z,relro -Wl,-z,now -shared -Wl,-soname,libnative-lib.so -o ../../../../build/intermediates/cmake/debug/obj/armeabi-v7a/libnative-lib.so CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o  -llog -lEGL -lGLESv2 -lm "/Users/alex/Library/Android/sdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/armeabi-v7a/libc++_static.a" "-latomic" && :

The obvious file .externalNativeBuild/cmake/debug/armeabi-v7a/cmake_build_output.txt does not contain interesting information (unless you have problems with CMake configuration per se). Gradle does not write this output to file, but you can use command line redirection, see Where are Gradle logs?.

Note: "-DCMAKE_VERBOSE_MAKEFILE:BOOL=ON" does not seem to work anymore. "-DCMAKE_VERBOSE_MAKEFILE=ON" worked for me. Not sure what has changed, I just installed android studio.