Preliminary Rust support (#1781)

* Add support for R_ARM_THM_MOVW_ABS_NC/THM_MOVT_ABS

These are sometimes emitted by the Rust LLVM compiler.

Ref: https://github.com/ARM-software/abi-aa/blob/main/aaelf32/aaelf32.rst#56relocation

* Discard LLVM bitcode from extension applications

LLVM-based compilers may include uncompressed bitcode in object files
to help with link-time optimization. However this can bloat binary sizes
from KB to MB.

* Expose alligned_malloc/free functions to applications

This is required to implement a global allocator in Rust.

firmware/targets/f7/application-ext.ld

@@ -48,5 +48,7 @@ SECTIONS
 	{
 		*(.comment)
 		*(.comment.*)
+		*(.llvmbc)
+		*(.llvmcmd)
 	}
 }