IssueTracker

OS: Windows 10
Android Studio: 2.3.1 Stable (also exists in 2.4 Preview 7)
JRE: 1.8.0_112
Gradle Version: 3.4.1
Build Tools Version: 25.0.2

Steps to Reproduce:
1. Create a module with native C++ code using NDK (or Google's NDK samples: https://github.com/googlesamples/android-ndk)
2. Add external build to module's gradle file
    externalNativeBuild {
        ndkBuild {
            path 'src/main/jni/Android.mk'
        }
    }
3. Android Studio > Build > Make Module (selected)
4. Build commands generated in mymodule/.externalNativeBuild/debug/armeabi-v7a/ndkBuild_build_command.txt

ISSUE: This file contains the build parameters for ndk-build (ndk-build.cmd) on Windows. However, the "NDK_OUT" param has the Windows path with backslashes, instead of forward slashes (inconsistent).

APP_BUILD_SCRIPT=C:\Users\AndroidUser\projects\sample\mymodule\src\main\jni\Android.mk
NDK_APPLICATION_MK=C:\Users\AndroidUser\projects\sample\mymodule\src\main\jni\Application.mk
NDK_OUT=C:/Users/AndroidUser/projects/sample/mymodule/build/intermediates/ndkBuild/debug/obj
NDK_LIBS_OUT=C:\Users\AndroidUser\projects\sample\mymodule\build\intermediates\ndkBuild\debug\lib

Running this command fails from the command line as is, however fixing the slashes on "NDK_OUT" allows manually generating the debug files for the native code.