Add test for remap-from in the form of $PWD/trailing

src/test/run-make-fulldeps/remap-path-prefix/Makefile

@@ -0,0 +1,6 @@
+-include ../tools.mk
+
+# Checks if remapping works if the remap-from string contains path to the working directory plus more
+all:
+	$(RUSTC) --remap-path-prefix $$PWD/auxiliary=/the/aux --crate-type=lib --emit=metadata auxiliary/lib.rs
+	! grep "$$PWD/auxiliary" $(TMPDIR)/liblib.rmeta || exit 1

src/test/run-make-fulldeps/remap-path-prefix/auxiliary/lib.rs

@@ -0,0 +1,3 @@
+fn lib() {
+    panic!("calm");
+}