[libc] Enable varargs tests for AMDGPU targets

Summary:
This reverts commit 574ab7e.

Author: jhuber6

libc/config/gpu/entrypoints.txt

@@ -1,3 +1,13 @@
+if(LIBC_TARGET_ARCHITECTURE_IS_AMDGPU)
+  set(extra_entrypoints
+      # stdio.h entrypoints
+      libc.src.stdio.sprintf
+      libc.src.stdio.snprintf
+      libc.src.stdio.vsprintf
+      libc.src.stdio.vsnprintf
+  )
+endif()
+
 set(TARGET_LIBC_ENTRYPOINTS
     # assert.h entrypoints
     libc.src.assert.__assert_fail
@@ -175,6 +185,7 @@ set(TARGET_LIBC_ENTRYPOINTS
     libc.src.errno.errno
 
     # stdio.h entrypoints
+    ${extra_entrypoints}
     libc.src.stdio.feof
     libc.src.stdio.ferror
     libc.src.stdio.fseek

libc/test/src/__support/CMakeLists.txt

@@ -86,8 +86,8 @@ add_libc_test(
     libc.src.__support.uint128
 )
 
-# The GPU does not support varargs currently.
-if(NOT LIBC_TARGET_OS_IS_GPU)
+# NVPTX does not support varargs currently.
+if(NOT LIBC_TARGET_ARCHITECTURE_IS_NVPTX)
   add_libc_test(
     arg_list_test
     SUITE