Fixed concatenation

Author: fzhinkin

core/common/src/files/Paths.kt

@@ -77,7 +77,7 @@ public fun Path(base: String, vararg parts: String): Path {
     return Path(buildString {
         append(base)
         parts.forEach {
-            if (!endsWith(Path.separator)) {
+            if (isNotEmpty() && !endsWith(Path.separator)) {
                 append(Path.separator)
             }
             append(it)

core/common/test/files/SmokeFileTest.kt

@@ -178,6 +178,9 @@ class SmokeFileTest {
             constructAbsolutePath("a", "b", "..", "c"),
             Path("${Path.separator}a", "b", "..${Path.separator}c").toString()
         )
+
+        assertEquals(constructRelativePath("a", "b", "c"),
+            Path("", "a", "b", "c").toString())
     }
 
     @Test