feat: unset declarationMap tsc option if present

As reported in
#768 (comment),
declarationMap flag may cause the compilation to error out if
declaration is set to false. The rationale is that it would be a bad
experience if tsc succeeds but tscc fails for no apparent reason.

packages/tscc/src/spec/TsccSpecWithTS.ts

@@ -155,10 +155,9 @@ export default class TsccSpecWithTS extends TsccSpec implements ITsccSpecWithTS
 			onWarning(`Incremental compilation is not supported. incremental flag is unset.`);
 			options.incremental = false;
 		}
-		if (options.declaration) {
-			// silently unset declaration flag
-			options.declaration = false;
-		}
+		// Silently unset flags related to declaration
+		options.declaration &&= false;
+		options.declarationMap &&= false;
 	}
 	private tsCompilerHost: ts.CompilerHost = ts.createCompilerHost(this.parsedConfig.options);
 	private constructor(

packages/tscc/test/spec/TsccSpecWithTS.ts

@@ -88,6 +88,17 @@ describe(`TsccSpecWithTS`, () => {
 				TsccSpecWithTS.pruneCompilerOptions(options2, noop);
 				expect(options2.target).toBeDefined();
 			}
+		});
+		test(`Unsets declaration and declarationMap`, () => {
+			{
+				const options: ts.CompilerOptions = {
+					declaration: true,
+					declarationMap: true
+				};
+				TsccSpecWithTS.pruneCompilerOptions(options, noop);
+				expect(options.declaration).toBeFalsy();
+				expect(options.declarationMap).toBeFalsy();
+			}
 		})
 	})
 });