Removes default visibility in debug mode and updates unit tests for alt_rsmi impl (#2091)

* Update unit tests for alt_rsmi impl

- Create distinct test executable for alt_rsmi testing
- Updated alt_rsmi tests to use public methods
- Compiles alt_rsmi.cc with ARSMI_TEST_BUILD
- Enables external linkage of internal variables
- Only for AltRsmiTests.cpp that manipulates internals
- Clean separation for test behavior

* Address review comments

* restore hidden symbol visibility

src/misc/alt_rsmi.cc

@@ -48,18 +48,29 @@ struct ARSMI_systemNode {
     std::string s_card;
 };
 
-static const char *kKFDNodesPathRoot = "/sys/class/kfd/kfd/topology/nodes";
+// Internal implementation details
+// When compiled into the test binary (ARSMI_TEST_BUILD defined), these have external linkage
+// so AltRsmiTestUtils.cpp can access them via extern declarations.
+// When compiled into the production library (ARSMI_TEST_BUILD not defined), these are static.
+#ifdef ARSMI_TEST_BUILD
+  // Test build: external linkage for cross-TU access
+  #define ARSMI_LOCAL thread_local
+#else
+  // Production build: static/internal linkage
+  #define ARSMI_LOCAL static thread_local
+#endif
+
+ARSMI_LOCAL const char *kKFDNodesPathRoot = "/sys/class/kfd/kfd/topology/nodes";
 static const uint32_t kAmdGpuId = 0x1002;
 
 // Vector containing data about each node, ordered by bdf ID
-static thread_local std::vector<ARSMI_systemNode> ARSMI_orderedNodes;
+ARSMI_LOCAL std::vector<ARSMI_systemNode> ARSMI_orderedNodes;
 
 // 2-D matrix with link information between each pair of nodes.
-static thread_local std::vector<std::vector<ARSMI_linkInfo>> ARSMI_orderedLinks;
+ARSMI_LOCAL std::vector<std::vector<ARSMI_linkInfo>> ARSMI_orderedLinks;
 
 // Number of devices recognized
-static thread_local int ARSMI_num_devices=-1;
-
+ARSMI_LOCAL int ARSMI_num_devices=-1;
 
 // Public API functions
 int ARSMI_init(void)