Fix JavaScript dependencies in bundles. (#4215)

Fixes #4602

We turned off `allowJs` by default, to keep the compiler from grabbing
a bunch of files that it wouldn't actually do anything useful with.  On
the other hand, this caused problems with bundles, where the compiler
needs to gather all the dependencies, including JavaScript ones.  This
fixes this so that when we are bundling, we analyse JavaScript imports
in the compiler.

cli/js/compiler_imports.ts

@@ -120,7 +120,7 @@ export function processLocalImports(
   sources: Record<string, string>,
   specifiers: Array<[string, string]>,
   referrer?: string,
-  checkJs = false
+  processJsImports = false
 ): string[] {
   if (!specifiers.length) {
     return [];
@@ -145,9 +145,9 @@ export function processLocalImports(
     if (!sourceFile.processed) {
       processLocalImports(
         sources,
-        sourceFile.imports(checkJs),
+        sourceFile.imports(processJsImports),
         sourceFile.url,
-        checkJs
+        processJsImports
       );
     }
   }
@@ -163,7 +163,7 @@ export function processLocalImports(
 export async function processImports(
   specifiers: Array<[string, string]>,
   referrer?: string,
-  checkJs = false
+  processJsImports = false
 ): Promise<string[]> {
   if (!specifiers.length) {
     return [];
@@ -179,9 +179,9 @@ export async function processImports(
     sourceFile.cache(specifiers[i][0], referrer);
     if (!sourceFile.processed) {
       await processImports(
-        sourceFile.imports(checkJs),
+        sourceFile.imports(processJsImports),
         sourceFile.url,
-        checkJs
+        processJsImports
       );
     }
   }