There is wrong keystore path in generated build.gradle using gradle build system on Windows, when the keystore path is manually edited in the projectsettings.asset (TestGradle>ProjectSettings>ProjectSettings.asset) in order not to be dependent on where project is stored between computers

How to reproduce:
1. Open the attached project "TestGradle" (located inside TestKeystore.zip)
2. Change platform to Android and set Gradle build system
3. Go to Android player settings and provide the password for the keystore ( Password in edit)
4. Build .apk file
5. Build fails because it could not compile build file "C:\Users\ievar\Downloads\TestKeystore\TestKeystore\TestGradle\../Builds/Keystore/TestKeyStore.jks"
6. Open file "build.gradle" inside the project directory ".../Temp/StagingArea/gradleOut/build.gradle"
7. Notice that Unity fills the keystore path with a mix of backslashes '\' and slashes '/' as shown in the attachment named "keystorePath.PNG"

This issue prevents users from building a release build for Android from a Windows computer

Reproducible: 5.5.0b1, 5.5.0p1, 5.6.0b2
Gradle introduced in 5.5
Note: it build just fine using Internal build system

Workaround: Set keystore path in editor