Scripting: fix string script source location

fixes proper script definition discovery for expressions and other
scripts created from a string.

plugins/scripting/scripting-compiler/tests/org/jetbrains/kotlin/scripting/compiler/plugin/ScriptingWithCliCompilerTest.kt

@@ -71,28 +71,20 @@ class ScriptingWithCliCompilerTest {
         runWithK2JVMCompiler(
             arrayOf(
                 "-cp", getMainKtsClassPath().joinToString(File.pathSeparator),
-                "-expression",
-                "\\@file:CompilerOptions(\"-Xunknown1\")"
+                "-expression=@file:CompilerOptions(\"-Xunknown1\")"
             ),
             expectedExitCode = 1,
             expectedSomeErrPatterns = listOf(
                 "unresolved reference: CompilerOptions"
             )
         )
-        // it seems not possible to make a one-liner with the annotation, and
-        // annotation is the easiest available distinguishing factor for the .main.kts script
-        // so, considering "expecting an element" error as a success here
         runWithK2JVMCompiler(
             arrayOf(
                 "-cp", getMainKtsClassPath().joinToString(File.pathSeparator),
                 "-Xdefault-script-extension=.main.kts",
-                "-expression",
-                "\\@file:CompilerOptions(\"-Xunknown1\")"
+                "-expression=@file:CompilerOptions(\"-Xunknown1\")"
             ),
-            expectedExitCode = 1,
-            expectedSomeErrPatterns = listOf(
-                "expecting an element"
-            )
+            expectedExitCode = 0,
         )
     }