Fix tests to match behaviour expected with newest toolchain

Newest toolchains contain the swift --> swift-frontend rename so a couple of tests needed fixing up.

Author: artemcm

Tests/SwiftDriverTests/JobExecutorTests.swift

@@ -192,7 +192,7 @@ final class JobExecutorTests: XCTestCase {
 
   func testSwiftDriverExecOverride() throws {
     var env = ProcessEnv.vars
-    let envVarName = "SWIFT_DRIVER_SWIFT_EXEC"
+    let envVarName = "SWIFT_DRIVER_SWIFT_FRONTEND_EXEC"
     let dummyPath = "/some/garbage/path/fnord"
     let executor = try SwiftDriverExecutor(diagnosticsEngine: DiagnosticsEngine(),
                                            processSet: ProcessSet(),
@@ -202,7 +202,7 @@ final class JobExecutorTests: XCTestCase {
     // DarwinToolchain
     env.removeValue(forKey: envVarName)
     let normalSwiftPath = try DarwinToolchain(env: env, executor: executor).getToolPath(.swiftCompiler)
-    XCTAssertEqual(normalSwiftPath.basenameWithoutExt, "swift")
+    XCTAssertEqual(normalSwiftPath.basenameWithoutExt, "swift-frontend")
 
     env[envVarName] = dummyPath
     let overriddenSwiftPath = try DarwinToolchain(env: env, executor: executor).getToolPath(.swiftCompiler)
@@ -211,7 +211,7 @@ final class JobExecutorTests: XCTestCase {
     // GenericUnixToolchain
     env.removeValue(forKey: envVarName)
     let unixSwiftPath = try GenericUnixToolchain(env: env, executor: executor).getToolPath(.swiftCompiler)
-    XCTAssertEqual(unixSwiftPath.basenameWithoutExt, "swift")
+    XCTAssertEqual(unixSwiftPath.basenameWithoutExt, "swift-frontend")
 
     env[envVarName] = dummyPath
     let unixOverriddenSwiftPath = try GenericUnixToolchain(env: env, executor: executor).getToolPath(.swiftCompiler)

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -1584,19 +1584,19 @@ final class SwiftDriverTests: XCTestCase {
     XCTAssertEqual(output,
     """
     digraph Jobs {
-      "compile (swiftc)" [style=bold];
+      "compile (swift-frontend)" [style=bold];
       "test.swift" [fontsize=12];
-      "test.swift" -> "compile (swiftc)" [color=blue];
+      "test.swift" -> "compile (swift-frontend)" [color=blue];
       "test.o" [fontsize=12];
-      "compile (swiftc)" -> "test.o" [color=green];
+      "compile (swift-frontend)" -> "test.o" [color=green];
       "test.swiftmodule" [fontsize=12];
-      "compile (swiftc)" -> "test.swiftmodule" [color=green];
+      "compile (swift-frontend)" -> "test.swiftmodule" [color=green];
       "test.swiftdoc" [fontsize=12];
-      "compile (swiftc)" -> "test.swiftdoc" [color=green];
-      "mergeModule (swiftc)" [style=bold];
-      "test.swiftmodule" -> "mergeModule (swiftc)" [color=blue];
-      "mergeModule (swiftc)" -> "test.swiftmodule" [color=green];
-      "mergeModule (swiftc)" -> "test.swiftdoc" [color=green];
+      "compile (swift-frontend)" -> "test.swiftdoc" [color=green];
+      "mergeModule (swift-frontend)" [style=bold];
+      "test.swiftmodule" -> "mergeModule (swift-frontend)" [color=blue];
+      "mergeModule (swift-frontend)" -> "test.swiftmodule" [color=green];
+      "mergeModule (swift-frontend)" -> "test.swiftdoc" [color=green];
       "link (\(dynamicLinker))" [style=bold];
       "test.o" -> "link (\(dynamicLinker))" [color=blue];
       "test" [fontsize=12];