Remove customizations for macOS on Apple Silicon

These tweaks used to be needed to work around [a Gradle
bug](gradle/gradle#18876).  That bug is still
open, but I find that all native components build and pass their tests
just fine without these hacks.

build.gradle.kts

@@ -28,7 +28,6 @@ repositories {
 }
 
 val osName: String by extra(System.getProperty("os.name"))
-val archName: String by extra(System.getProperty("os.arch"))
 val isWindows by extra(osName.startsWith("Windows "))
 
 JavaVersion.current().let {

cast/cast/build.gradle.kts

@@ -8,13 +8,6 @@ plugins {
 }
 
 library {
-  // Temporary change to build on M1 Mac machines, until
-  // https://github.com/gradle/gradle/issues/18876
-  // is fixed
-  if (rootProject.extra["osName"] == "Mac OS X" && rootProject.extra["archName"] == "aarch64") {
-    targetMachines.add(machines.macOS.x86_64)
-  }
-
   binaries.whenElementFinalized {
     compileTask.get().configure(closureOf<CppCompile> { macros["BUILD_CAST_DLL"] = "1" })
 

cast/smoke_main/build.gradle.kts

@@ -47,13 +47,6 @@ val xlatorTestDebugSharedLibraryConfig = createXlatorConfig(false)
 val xlatorTestReleaseSharedLibraryConfig = createXlatorConfig(true)
 
 application {
-  // Temporary change to build on M1 Mac machines, until
-  // https://github.com/gradle/gradle/issues/18876
-  // is fixed
-  if (rootProject.extra["osName"] == "Mac OS X" && rootProject.extra["archName"] == "aarch64") {
-    targetMachines.add(machines.macOS.x86_64)
-  }
-
   dependencies {
     coreResources(projects.core)
     smokeMainExtraPathElements(projects.cast)

cast/xlator_test/build.gradle.kts

@@ -13,12 +13,6 @@ dependencies {
 }
 
 library {
-  // Temporary change to build on M1 Mac machines, until
-  // https://github.com/gradle/gradle/issues/18876
-  // is fixed
-  if (rootProject.extra["osName"] == "Mac OS X" && rootProject.extra["archName"] == "aarch64") {
-    targetMachines.add(machines.macOS.x86_64)
-  }
   privateHeaders.from(castHeaderDirectory)
 
   dependencies { implementation(projects.cast.cast) }