Revert CMake: Make most target symbols hidden by default

This reverts r362990 (git commit 374571301dc8e9bc9fdd1d70f86015de198673bd)

This was causing linker warnings on Darwin:

ld: warning: direct access in function 'llvm::initializeEvexToVexInstPassPass(llvm::PassRegistry&)'
from file '../../lib/libLLVMX86CodeGen.a(X86EvexToVex.cpp.o)' to global weak symbol
'void std::__1::__call_once_proxy<std::__1::tuple<void* (&)(llvm::PassRegistry&),
std::__1::reference_wrapper<llvm::PassRegistry>&&> >(void*)' from file '../../lib/libLLVMCore.a(Verifier.cpp.o)'
means the weak symbol cannot be overridden at runtime. This was likely caused by different translation
units being compiled with different visibility settings.

llvm-svn: 363028
diff --git a/llvm/lib/Target/Sparc/SparcTargetMachine.cpp b/llvm/lib/Target/Sparc/SparcTargetMachine.cpp
index 80f09c0..195cff7 100644
--- a/llvm/lib/Target/Sparc/SparcTargetMachine.cpp
+++ b/llvm/lib/Target/Sparc/SparcTargetMachine.cpp
@@ -20,7 +20,7 @@
 #include "llvm/Support/TargetRegistry.h"
 using namespace llvm;
 
-extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeSparcTarget() {
+extern "C" void LLVMInitializeSparcTarget() {
   // Register the target.
   RegisterTargetMachine<SparcV8TargetMachine> X(getTheSparcTarget());
   RegisterTargetMachine<SparcV9TargetMachine> Y(getTheSparcV9Target());