Tests: Add missing -target clang flags in @cdecl Interpreter tests

rdar://155013885

Author: xymus

test/Interpreter/cdecl_official_run.swift

@@ -8,7 +8,7 @@
 // RUN:   -enable-experimental-feature CDecl
 
 /// Build and run a binary from Swift and C code.
-// RUN: %clang-no-modules -c %t/Client.c -o %t/Client.o \
+// RUN: %clang-no-modules -c %t/Client.c -o %t/Client.o -target %target-triple \
 // RUN:   -I %t -I %clang-include-dir -Werror -isysroot %sdk
 // RUN: %target-build-swift %t/Lib.swift %t/Client.o -O -o %t/a.out \
 // RUN:   -enable-experimental-feature CDecl -parse-as-library