FreeBSD: PIC cdecl_official_run.swift Client.o

Swift defaults to PIC everywhere. The Swift toolchain clang emits PIC
relocatable objects by default without passing `-fPIC` on Linux, so the
emitted Client.o is relocatable. This is not the case on FreeBSD, where
clang uses the static relocation model by default resulting in a link
failure due to mixing relocations with non-relocatable objects.

```
ld.lld: error: relocation R_X86_64_64 cannot be used against local symbol; recompile with -fPIC
```

Passing `-fPIC` where needed.

Author: etcwilde

test/Interpreter/cdecl_official_run.swift

@@ -9,7 +9,7 @@
 
 /// Build and run a binary from Swift and C code.
 // 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-pic-opt -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
 // RUN: %target-codesign %t/a.out