[libc] Add GPU config file using the new format (llvm#66635)

Summary:
This patch copies a config file for the GPU similar to the
baremetal/embedded implementation. This will configure the
implementations of functions like `sprintf` and `snprintf` to be
compiled into more simple versions that can be run on the GPU. These
functions cannot be enabled yet as Vararg support hasn't landed, but it
will be used then.

Author: jhuber6

libc/config/gpu/config.json

@@ -0,0 +1,16 @@
+{
+  "printf": {
+    "LIBC_CONF_PRINTF_DISABLE_FLOAT": {
+      "value": true
+    },
+    "LIBC_CONF_PRINTF_DISABLE_INDEX_MODE": {
+      "value": true
+    },
+    "LIBC_CONF_PRINTF_DISABLE_WRITE_INT": {
+      "value": true
+    },
+    "LIBC_CONF_PRINTF_FLOAT_TO_STR_USE_MEGA_LONG_DOUBLE_TABLE": {
+      "value": false
+    }
+  }
+}