Parse out the line continuation character at the end of lines (#659)

* make sure we only match for end of line

* handle line continuation characters

* fix the order and repair the parsing of backslash that was already there

CHANGELOG.md

@@ -20,6 +20,7 @@ Bug Fixes:
 Improvements:
 
 - Update signing to support VSCode extension signing. [#647](https://github.com/microsoft/vscode-makefile-tools/pull/647)
+- Handle line continuation characters during parsing. [#628](https://github.com/microsoft/vscode-makefile-tools/issues/628)
 
 ## 0.10.26
 

src/parser.ts

@@ -189,7 +189,7 @@ export async function preprocessDryRunOutput(
   // Some compiler/linker commands are split on multiple lines.
   // At the end of every intermediate line is at least a space, then a \ and end of line.
   // Concatenate all these lines to see clearly each command on one line.
-  let regexp: RegExp = /\s+\\$\n/gm;
+  let regexp: RegExp = /(\\$\n)|(\\\\$\n)/gm;
   preprocessTasks.push(function (): void {
     preprocessedDryRunOutputStr = preprocessedDryRunOutputStr.replace(
       regexp,