Add reproducibility test for -emit-bc

Author: practicalswift

test/reproducible-builds/swift-emit-bc.swift

@@ -0,0 +1,10 @@
+// RUN: rm -rf %t && mkdir -p %t
+// NOTE: We need to re-use the output filename ("-o run.bc") between the two
+//       runs since the LLVM BC file contains the filename specified:
+//       <UnknownCode16 ... /> record string = 'run.bc'
+// RUN: %target-build-swift -O -g -module-name foo -emit-bc %s -o %t/run.bc
+// RUN: mv %t/run.bc %t/run-1.bc
+// RUN: %target-build-swift -O -g -module-name foo -emit-bc %s -o %t/run.bc
+// RUN: mv %t/run.bc %t/run-2.bc
+// RUN: cmp %t/run-1.bc %t/run-2.bc
+print("foo")