Add a declaration for __cpuid for the IntelLLVM compiler.

Imported from GitHub PR https://github.com/abseil/abseil-cpp/pull/1452

__cpuid is declared in intrin.h, but is excluded on non-Windows platforms.
We add this declaration to compensate.

Fixes #1358

PiperOrigin-RevId: 534449804
Change-Id: I91027f79d8d52c4da428d5c3a53e2cec00825c13

absl/crc/internal/cpu_detect.cc

@@ -28,15 +28,12 @@
 #include <intrin.h>
 #endif
 
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-namespace crc_internal {
-
 #if defined(__x86_64__) || defined(_M_X64)
-
-namespace {
-
-#if !defined(_WIN32) && !defined(_WIN64)
+#if ABSL_HAVE_BUILTIN(__cpuid)
+// MSVC-equivalent __cpuid intrinsic declaration for clang-like compilers
+// for non-Windows build environments.
+extern void __cpuid(int[4], int);
+#elif !defined(_WIN32) && !defined(_WIN64)
 // MSVC defines this function for us.
 // https://learn.microsoft.com/en-us/cpp/intrinsics/cpuid-cpuidex
 static void __cpuid(int cpu_info[4], int info_type) {
@@ -46,6 +43,15 @@ static void __cpuid(int cpu_info[4], int info_type) {
                    : "a"(info_type), "c"(0));
 }
 #endif  // !defined(_WIN32) && !defined(_WIN64)
+#endif  // defined(__x86_64__) || defined(_M_X64)
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace crc_internal {
+
+#if defined(__x86_64__) || defined(_M_X64)
+
+namespace {
 
 enum class Vendor {
   kUnknown,

absl/random/internal/randen_detect.cc

@@ -45,6 +45,10 @@
 #if defined(ABSL_INTERNAL_USE_X86_CPUID)
 #if defined(_WIN32) || defined(_WIN64)
 #include <intrin.h>  // NOLINT(build/include_order)
+#elif ABSL_HAVE_BUILTIN(__cpuid)
+// MSVC-equivalent __cpuid intrinsic declaration for clang-like compilers
+// for non-Windows build environments.
+extern void __cpuid(int[4], int);
 #else
 // MSVC-equivalent __cpuid intrinsic function.
 static void __cpuid(int cpu_info[4], int info_type) {