Use ComposeSettings#getEnvironment only as env variables override map

Reading all the environment variables at configuration time leads to marking each of them as configuration cache input, so Gradle will detect value changes and invalidate cache on any irrelevant variable value change
#307

Author: ALikhachev

src/main/groovy/com/avast/gradle/dockercompose/ComposeExecutor.groovy

@@ -46,7 +46,7 @@ class ComposeExecutor {
             if (settings.dockerComposeWorkingDirectory.isPresent()) {
                 e.setWorkingDir(settings.dockerComposeWorkingDirectory.get().asFile)
             }
-            e.environment = settings.environment.get()
+            e.environment = System.getenv() + settings.environment.get()
             def finalArgs = [settings.executable.get()]
             finalArgs.addAll(settings.composeAdditionalArgs.get())
             if (noAnsi) {

src/main/groovy/com/avast/gradle/dockercompose/ComposeSettings.groovy

@@ -168,7 +168,6 @@ abstract class ComposeSettings {
             executable.set('docker-compose')
             dockerExecutable.set('docker')
         }
-        environment.set(System.getenv())
         dockerComposeStopTimeout.set(Duration.ofSeconds(10))
 
         this.containerLogToDir.set(project.buildDir.toPath().resolve('containers-logs').toFile())

src/main/groovy/com/avast/gradle/dockercompose/DockerExecutor.groovy

@@ -25,7 +25,7 @@ class DockerExecutor {
         def settings = this.settings
         new ByteArrayOutputStream().withStream { os ->
             def er = exec.exec { ExecSpec e ->
-                e.environment = settings.environment.get()
+                e.environment = System.getenv() + settings.environment.get()
                 def finalArgs = [settings.dockerExecutable.get()]
                 finalArgs.addAll(args)
                 e.commandLine finalArgs