Add sep variable to compiletest headers

Author: djkoloski

src/tools/compiletest/src/header.rs

@@ -793,6 +793,7 @@ impl Config {
 
 fn expand_variables(mut value: String, config: &Config) -> String {
     const CWD: &str = "{{cwd}}";
+    const SEP: &str = "{{sep}}";
     const SRC_BASE: &str = "{{src-base}}";
     const BUILD_BASE: &str = "{{build-base}}";
 
@@ -801,6 +802,10 @@ fn expand_variables(mut value: String, config: &Config) -> String {
         value = value.replace(CWD, &cwd.to_string_lossy());
     }
 
+    if value.contains(SEP) {
+        value = value.replace(SEP, std::path::MAIN_SEPARATOR_STR);
+    }
+
     if value.contains(SRC_BASE) {
         value = value.replace(SRC_BASE, &config.src_base.to_string_lossy());
     }

tests/ui/shell-argfiles/shell-argfiles-badquotes.rs

@@ -1,6 +1,6 @@
 // Check to see if we can get parameters from an @argsfile file
 //
-// compile-flags: --cfg cmdline_set -Z shell-argfiles @shell:{{src-base}}/shell-argfiles/shell-argfiles-badquotes.args
+// compile-flags: --cfg cmdline_set -Z shell-argfiles @shell:{{src-base}}{{sep}}shell-argfiles/shell-argfiles-badquotes.args
 
 fn main() {
 }