[Libomptarget] Fix external visibility for internal variables

After the changes in D117362 made variables declared inside of a target
declare directive visible outside the plugin, some variables inside the
runtime were given visiblity that conflicted with their address space
type. This caused problems when shared or local memory was made
externally visible. This patch fixes this issue by making these
varialbes static within the module, therefore limiting their visibility
to being internal.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D117526

openmp/libomptarget/DeviceRTL/include/Types.h

@@ -193,7 +193,8 @@ enum OMPTgtExecModeFlags : int8_t {
 // TODO: clang should use address space 5 for omp_thread_mem_alloc, but right
 //       now that's not the case.
 #define THREAD_LOCAL(NAME)                                                     \
-  NAME [[clang::loader_uninitialized, clang::address_space(5)]]
+  NAME [[clang::loader_uninitialized, clang::address_space(5),                 \
+         gnu::visibility("hidden")]]
 
 // TODO: clang should use address space 4 for omp_const_mem_alloc, maybe it
 //       does?

openmp/libomptarget/DeviceRTL/src/Workshare.cpp

@@ -46,7 +46,7 @@ struct DynamicScheduleTracker {
 #pragma omp declare target
 
 // TODO: This variable is a hack inherited from the old runtime.
-uint64_t SHARED(Cnt);
+static uint64_t SHARED(Cnt);
 
 template <typename T, typename ST> struct omptarget_nvptx_LoopSupport {
   ////////////////////////////////////////////////////////////////////////////////
@@ -443,7 +443,7 @@ template <typename T, typename ST> struct omptarget_nvptx_LoopSupport {
 
 // TODO: This is a stopgap. We probably want to expand the dispatch API to take
 //       an DST pointer which can then be allocated properly without malloc.
-DynamicScheduleTracker *THREAD_LOCAL(ThreadDSTPtr);
+static DynamicScheduleTracker *THREAD_LOCAL(ThreadDSTPtr);
 
 // Create a new DST, link the current one, and define the new as current.
 static DynamicScheduleTracker *pushDST() {