Use project directory as a base for stdlib js build

Some sources for kotlin-stdlib-js-ir are not copied to build dir
and used directly from the project.

Modify kotlin.test/js-ir as well, while there's no evidence of the
problem so far.

Should be removed after KT-50876 fix.

^KTI-730 In Progress

libraries/kotlin.test/js-ir/build.gradle.kts

@@ -55,7 +55,7 @@ tasks.withType<KotlinCompile<*>>().configureEach {
 
     doFirst {
         kotlinOptions.freeCompilerArgs += listOfNotNull(
-            "-Xklib-relative-path-base=$buildDir".takeIf { !kotlinBuildProperties.getBoolean("kotlin.build.use.absolute.paths.in.klib") }
+            "-Xklib-relative-path-base=$buildDir,$projectDir".takeIf { !kotlinBuildProperties.getBoolean("kotlin.build.use.absolute.paths.in.klib") }
         )
     }
 }

libraries/stdlib/js-ir/build.gradle.kts

@@ -146,7 +146,7 @@ tasks.withType<KotlinCompile<*>>().configureEach {
 
     doFirst {
         kotlinOptions.freeCompilerArgs += listOfNotNull(
-            "-Xklib-relative-path-base=$buildDir".takeIf { !kotlinBuildProperties.getBoolean("kotlin.build.use.absolute.paths.in.klib") }
+            "-Xklib-relative-path-base=$buildDir,$projectDir".takeIf { !kotlinBuildProperties.getBoolean("kotlin.build.use.absolute.paths.in.klib") }
         )
     }
 }