[test] Add a Linux test for indirect link dependencies relying on -L.

This is the Linux equivalent of 3731a2f. There's probably a way to
merge them into one file cleanly, but the extra linker args on OS X
make it a little tricky. I'm deciding not to worry about it right now.

Author: jrose-apple

validation-test/execution/interpret-with-dependencies-linux.swift

@@ -0,0 +1,26 @@
+// REQUIRES: OS=linux-gnu
+// RUN: rm -rf %t && mkdir %t
+
+// RUN: echo 'int abc = 42;' | %clang -x c - -shared -fPIC -o %t/libabc.so
+// RUN: echo 'int test() { extern int abc; return abc; }' | %clang -x c - -L%t -shared -fPIC -labc -o %t/libfoo.so
+
+// RUN: %swift_driver -I %S/Inputs/custom-modules -L%t %s | FileCheck %s
+// CHECK: {{okay}}
+
+// Now test a dependency on a library in the compiler's resource directory.
+// RUN: mkdir -p %t/rsrc/%target-sdk-name/
+// RUN: ln -s %t/libabc.so %t/rsrc/%target-sdk-name/
+// RUN: ln -s %platform-module-dir/../* %t/rsrc/%target-sdk-name/
+// RUN: ln -s %platform-module-dir/../../shims %t/rsrc/
+// RUN: mkdir -p %t/other
+// RUN: ln -s %t/libfoo.so %t/other
+
+// RUN: %swift_driver -I %S/Inputs/custom-modules -L%t/other -resource-dir %t/rsrc/ %s | FileCheck %s
+
+import foo
+
+if test() == 42 {
+  print("okay")
+} else {
+  print("problem")
+}