Allow assertion to omit trimming whitespace

Author: kimdv

Tests/SwiftSyntaxBuilderTest/Assertions.swift

@@ -16,10 +16,10 @@ import _SwiftSyntaxTestSupport
 
 import XCTest
 
-func AssertBuildResult<T: SyntaxProtocol>(_ buildable: T, _ expectedResult: String, file: StaticString = #file, line: UInt = #line) {
+func AssertBuildResult<T: SyntaxProtocol>(_ buildable: T, _ expectedResult: String, trimTrailingWhitespace: Bool = true, file: StaticString = #file, line: UInt = #line) {
   AssertStringsEqualWithDiff(
-    buildable.formatted().description.trimmingTrailingWhitespace(),
-    expectedResult.trimmingTrailingWhitespace(),
+    trimTrailingWhitespace ? buildable.formatted().description.trimmingTrailingWhitespace() : buildable.formatted().description,
+    trimTrailingWhitespace ? expectedResult.trimmingTrailingWhitespace() : expectedResult,
     file: file,
     line: line
   )