Fix rust-native build issue when debug is enabled

When DEBUG_BUILD is set for building rust-native, it generated
error as follows:-
=========================================================
Building : rustdoc, rustdoc-json-types
error[E0463]: can't find crate for `rustc_llvm`
which `rustc_driver` depends on
  --> src/librustdoc/lib.rs:37:1
   |
37 | extern crate rustc_driver;
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^ can't find crate
=========================================================
On analyzing the issue, it was found that rustc_llvm crate was present
at required path. However, it was very huge due to the presence of
debugging information. Hence, it was somehow not recognized as a valid
crate. The following patch removes the debug information from
rust-llvm-native which is built prior to rust-native but retains debug
information as required in rust-native binaries.

(From OE-Core rev: 7261a4b4d5778a48c8d72c9125233b1b0bc009e6)

Signed-off-by: Pgowda <pgowda.cve@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/rust/rust-llvm.inc

@@ -15,6 +15,11 @@ DEPENDS += "ninja-native rust-llvm-native"
 ARM_INSTRUCTION_SET:armv5 = "arm"
 ARM_INSTRUCTION_SET:armv4t = "arm"
 
+# rustc_llvm with debug info is not recognized as a valid crate that's
+# generated by rust-llvm-native.
+CFLAGS:remove = "-g"
+CXXFLAGS:remove = "-g"
+
 LLVM_DIR = "llvm${LLVM_RELEASE}"
 
 EXTRA_OECMAKE = " \