[build] Clean up Gradle configs (#5685)

Putting an early exit if statement at the top instead of wrapping the
whole file contents unbreaks unit test configs, as was discovered for
SysId. It reduces nesting as well.

Unused plugins were removed from the beginnings of files as well.

simulation/halsim_ds_socket/build.gradle

@@ -1,3 +1,7 @@
+if (project.hasProperty('onlylinuxathena')) {
+    return;
+}
+
 description = "A plugin that listens on a socket so that you can use the real Driver Station software to connect to the simulation"
 
 ext {
@@ -7,7 +11,6 @@ ext {
 
 apply plugin: 'google-test-test-suite'
 
-
 ext {
     staticGtestConfigs = [:]
 }
@@ -17,28 +20,22 @@ apply from: "${rootDir}/shared/googletest.gradle"
 
 apply from: "${rootDir}/shared/plugins/setupBuild.gradle"
 
-
 model {
     testSuites {
-        def comps = $.components
-        if (!project.hasProperty('onlylinuxathena')) {
-            "${pluginName}Test"(GoogleTestTestSuiteSpec) {
-                for(NativeComponentSpec c : comps) {
-                    if (c.name == pluginName) {
-                        testing c
-                        break
-                    }
+        "${pluginName}Test"(GoogleTestTestSuiteSpec) {
+            for(NativeComponentSpec c : $.components) {
+                if (c.name == pluginName) {
+                    testing c
+                    break
                 }
-                sources {
-                    cpp {
-                        source {
-                            srcDirs 'src/test/native/cpp'
-                            include '**/*.cpp'
-                        }
-                        exportedHeaders {
-                            srcDirs 'src/test/native/include', 'src/main/native/cpp'
-                        }
-                    }
+            }
+            sources.cpp {
+                source {
+                    srcDirs 'src/test/native/cpp'
+                    include '**/*.cpp'
+                }
+                exportedHeaders {
+                    srcDirs 'src/test/native/include', 'src/main/native/cpp'
                 }
             }
         }