[test] Fix validation-test/Driver/many-inputs.swift harder.

We still need a valid SDK because we're making sure linking works too.

rdar://problem/25617239

Author: jrose-apple

validation-test/Driver/many-inputs.swift

@@ -3,18 +3,19 @@
 // This limit was chosen because multi-threaded compilation broke here on OS X
 // at one point.
 // RUN: for i in {1..1100}; do echo "public func foo$i() {}" > %t/$i.swift; echo "CHECK: foo$i" >> %t/check.txt; done
+// RUN: false
 
 // We're not using %target-swift-build because we don't want to run into any
 // limits *xcrun* has on arguments.
-// RUN: %swiftc_driver -sdk "" -target %target-triple -force-single-frontend-invocation -emit-library %t/*.swift -o %t/libWMO
+// RUN: %swiftc_driver -sdk %sdk -target %target-triple -force-single-frontend-invocation -emit-library %t/*.swift -o %t/libWMO
 // RUN: nm %t/libWMO | FileCheck %t/check.txt
 
-// RUN: %swiftc_driver -sdk "" -target %target-triple -force-single-frontend-invocation -num-threads 1 -emit-library %t/*.swift -o %t/libWMOThreaded
+// RUN: %swiftc_driver -sdk %sdk -target %target-triple -force-single-frontend-invocation -num-threads 1 -emit-library %t/*.swift -o %t/libWMOThreaded
 // RUN: nm %t/libWMOThreaded | FileCheck %t/check.txt
 
 // This is very slow due to process overhead. It's also doing one file at a time
 // because we don't have a good way for lit tests to claim more than one thread.
 // But it's still important to check.
-// RUN: %swiftc_driver -sdk "" -target %target-triple -emit-library %t/*.swift -o %t/libMultiFile
+// RUN: %swiftc_driver -sdk %sdk -target %target-triple -emit-library %t/*.swift -o %t/libMultiFile
 // RUN: nm %t/libMultiFile | FileCheck %t/check.txt