[libc] Allow NVPTX to use aliases

[jhuber6]

Summary

Summrary:
Following D156014 we can now use aliases for NVPTX, removing this source
of divergence. We require at least +ptx63 and at least sm_30 for
.alias but this is already within what we build for with libc
support.

libc/src/__support/common.h

 
 #include "src/__support/macros/attributes.h"
 #include "src/__support/macros/properties/architectures.h"
 
 #ifndef LLVM_LIBC_FUNCTION_ATTR
 #define LLVM_LIBC_FUNCTION_ATTR
 #endif
 
-// The NVPTX target does not support aliasing.
-#if defined(LIBC_COPT_PUBLIC_PACKAGING) && defined(LIBC_TARGET_ARCH_IS_NVPTX)
-#define LLVM_LIBC_FUNCTION_IMPL(type, name, arglist)                           \
-  LLVM_LIBC_FUNCTION_ATTR decltype(__llvm_libc::name)                          \
-      __##name##_impl__ __asm__(#name);                                        \
-  type __##name##_impl__ arglist
 // MacOS needs to be excluded because it does not support aliasing.
-#elif defined(LIBC_COPT_PUBLIC_PACKAGING) && (!defined(__APPLE__))
+#if defined(LIBC_COPT_PUBLIC_PACKAGING) && (!defined(__APPLE__))
 #define LLVM_LIBC_FUNCTION_IMPL(type, name, arglist)                           \
   LLVM_LIBC_FUNCTION_ATTR decltype(__llvm_libc::name)                          \
       __##name##_impl__ __asm__(#name);                                        \
   decltype(__llvm_libc::name) name [[gnu::alias(#name)]];                      \
   type __##name##_impl__ arglist
 #else
 #define LLVM_LIBC_FUNCTION_IMPL(type, name, arglist) type name arglist
 #endif