Remove extra trailing newline in preprocessor.js output (emscripten-c…

…ore#19574)

There were two different causes of extra newlines here.

.eslintrc.yml

@@ -7,6 +7,7 @@ extends:
 parserOptions:
   ecmaVersion: 12
 ignorePatterns:
+  - "out/"
   - "site/"
   - "cache/"
   - "third_party/"

src/parseTools.js

@@ -61,6 +61,11 @@ function preprocess(filename) {
   const isHtml = (fileExt === 'html' || fileExt === 'htm') ? true : false;
   let inStyle = false;
   const lines = text.split('\n');
+  // text.split yields an extra empty element at the end if text itself ends with a newline.
+  if (!lines[lines.length - 1]) {
+    lines.pop();
+  }
+
   let ret = '';
   let emptyLine = false;
 

test/other/test_unoptimized_code_size.js.size

@@ -1 +1 @@
-59358
+59351

test/other/test_unoptimized_code_size_no_asserts.js.size

@@ -1 +1 @@
-33006
+33001

test/other/test_unoptimized_code_size_strict.js.size

@@ -1 +1 @@
-58324
+58317

tools/preprocessor.js

@@ -10,7 +10,7 @@
 // Parameters:
 //    setting file.  Can specify 'settings.js' here, alternatively create a temp
 //                   file with modified settings and supply the filename here.
-//    shell file     This is the file that will be processed by the preprocessor
+//    input file     This is the file that will be processed by the preprocessor
 
 'use strict';
 
@@ -51,14 +51,13 @@ global.load = (f) => {
 };
 
 const settingsFile = arguments_[0];
-const shellFile = arguments_[1];
+const inputFile = arguments_[1];
 const expandMacros = arguments_.includes('--expandMacros');
 
 load(settingsFile);
 load('utility.js');
 load('modules.js');
 load('parseTools.js');
 
-const toHTML = expandMacros ? processMacros(preprocess(shellFile)) : preprocess(shellFile);
-
-print(toHTML);
+const output = expandMacros ? processMacros(preprocess(inputFile)) : preprocess(inputFile);
+process.stdout.write(output);