Fix a missing "-rpath", and add tests

Author: jrose-apple

lib/Driver/DarwinToolChains.cpp

@@ -376,6 +376,7 @@ toolchains::Darwin::addArgsToLinkStdlib(ArgStringList &Arguments,
       // frozen swift-in-OS libraries in the usr/lib/swift location. That's the
       // best we can give for rpath, though it might fail at runtime if the
       // support package isn't installed.
+      Arguments.push_back("-rpath");
       Arguments.push_back(context.Args.MakeArgString("/usr/lib/swift"));
     }
   }

test/Driver/linker-rpath.swift

@@ -0,0 +1,46 @@
+// REQUIRES: OS=macosx
+// Note: This is really about the /host/ environment, but since there are RUN
+// lines for multiple targets anyway it doesn't make a huge difference.
+
+// RUN: %swiftc_driver_plain -driver-print-jobs -target x86_64-apple-macosx10.9 %S/../Inputs/empty.swift | %FileCheck -check-prefix RPATH %s
+// RUN: %swiftc_driver_plain -driver-print-jobs -target x86_64-apple-macosx10.14 %S/../Inputs/empty.swift | %FileCheck -check-prefix RPATH %s
+// RUN: %swiftc_driver_plain -driver-print-jobs -target x86_64-apple-macosx10.14.3 %S/../Inputs/empty.swift | %FileCheck -check-prefix RPATH %s
+// RUN: %swiftc_driver_plain -driver-print-jobs -target x86_64-apple-macosx10.14.4 %S/../Inputs/empty.swift | %FileCheck -check-prefix RPATH %s
+// RUN: %swiftc_driver_plain -driver-print-jobs -target x86_64-apple-macosx10.15 %S/../Inputs/empty.swift | %FileCheck -check-prefix NO-RPATH %s
+
+// RUN: %swiftc_driver_plain -driver-print-jobs -target arm64-apple-ios12 %S/../Inputs/empty.swift | %FileCheck -check-prefix RPATH %s
+// RUN: %swiftc_driver_plain -driver-print-jobs -target arm64-apple-ios12.1 %S/../Inputs/empty.swift | %FileCheck -check-prefix RPATH %s
+// RUN: %swiftc_driver_plain -driver-print-jobs -target arm64-apple-ios12.2 %S/../Inputs/empty.swift | %FileCheck -check-prefix NO-RPATH %s
+// RUN: %swiftc_driver_plain -driver-print-jobs -target arm64-apple-ios13 %S/../Inputs/empty.swift | %FileCheck -check-prefix NO-RPATH %s
+
+// RUN: %swiftc_driver_plain -driver-print-jobs -target arm64-apple-tvos12 %S/../Inputs/empty.swift | %FileCheck -check-prefix RPATH %s
+// RUN: %swiftc_driver_plain -driver-print-jobs -target arm64-apple-tvos12.1 %S/../Inputs/empty.swift | %FileCheck -check-prefix RPATH %s
+// RUN: %swiftc_driver_plain -driver-print-jobs -target arm64-apple-tvos12.2 %S/../Inputs/empty.swift | %FileCheck -check-prefix NO-RPATH %s
+// RUN: %swiftc_driver_plain -driver-print-jobs -target arm64-apple-tvos13 %S/../Inputs/empty.swift | %FileCheck -check-prefix NO-RPATH %s
+
+// RUN: %swiftc_driver_plain -driver-print-jobs -target armv7k-apple-watchos5 %S/../Inputs/empty.swift | %FileCheck -check-prefix RPATH %s
+// RUN: %swiftc_driver_plain -driver-print-jobs -target armv7k-apple-watchos5.1 %S/../Inputs/empty.swift | %FileCheck -check-prefix RPATH %s
+// RUN: %swiftc_driver_plain -driver-print-jobs -target armv7k-apple-watchos5.2 %S/../Inputs/empty.swift | %FileCheck -check-prefix NO-RPATH %s
+// RUN: %swiftc_driver_plain -driver-print-jobs -target armv7k-apple-watchos6 %S/../Inputs/empty.swift | %FileCheck -check-prefix NO-RPATH %s
+
+// RPATH: bin/ld{{"? }}
+// RPATH-SAME: -rpath {{"?/usr/lib/swift(-.+)?"? }}
+// RPATH-SAME: -o {{[^ ]+}}
+
+// NO-RPATH-NOT: -rpath{{ }}
+
+// ### Test with -static-stdlib
+// RUN: %swiftc_driver_plain -driver-print-jobs -target x86_64-apple-macosx10.9 %S/../Inputs/empty.swift -static-stdlib | %FileCheck -check-prefix NO-RPATH %s
+// RUN: %swiftc_driver_plain -driver-print-jobs -target x86_64-apple-macosx10.15 %S/../Inputs/empty.swift -static-stdlib | %FileCheck -check-prefix NO-RPATH %s
+
+// ### Test with -no-stdlib-rpath
+// RUN: %swiftc_driver_plain -driver-print-jobs -target x86_64-apple-macosx10.9 %S/../Inputs/empty.swift -no-stdlib-rpath | %FileCheck -check-prefix NO-RPATH %s
+// RUN: %swiftc_driver_plain -driver-print-jobs -target x86_64-apple-macosx10.15 %S/../Inputs/empty.swift -no-stdlib-rpath | %FileCheck -check-prefix NO-RPATH %s
+
+// ### Test with -toolchain-stdlib-rpath
+// RUN: %swiftc_driver_plain -driver-print-jobs -toolchain-stdlib-rpath -target x86_64-apple-macosx10.9 %S/../Inputs/empty.swift -resource-dir garbage/ | %FileCheck -check-prefix TOOLCHAIN-RPATH -DPLATFORM=%target-sdk-name %s
+// RUN: %swiftc_driver_plain -driver-print-jobs -toolchain-stdlib-rpath -target x86_64-apple-macosx10.15 %S/../Inputs/empty.swift -resource-dir garbage/ | %FileCheck -check-prefix TOOLCHAIN-RPATH -DPLATFORM=%target-sdk-name %s
+
+// TOOLCHAIN-RPATH: bin/ld{{"? }}
+// TOOLCHAIN-RPATH-SAME: -rpath garbage/[[PLATFORM]]{{ }}
+// TOOLCHAIN-RPATH-SAME: -o {{[^ ]+}}