samples: rust: fix rust_print build making it a combined module

The `rust_print` module, when built as a module, fails to build with:

    ERROR: modpost: missing MODULE_LICENSE() in samples/rust/rust_print_events.o
    ERROR: modpost: "__tracepoint_rust_sample_loaded" [samples/rust/rust_print.ko] undefined!
    ERROR: modpost: "rust_do_trace_rust_sample_loaded" [samples/rust/rust_print.ko] undefined!

Fix it by building it as a combined one.

Cc: Masami Hiramatsu <[email protected]>
Cc: Alex Gaynor <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Gary Guo <[email protected]>
Cc: Björn Roy Baron <[email protected]>
Cc: Benno Lossin <[email protected]>
Cc: Andreas Hindborg <[email protected]>
Cc: Alice Ryhl <[email protected]>
Cc: Trevor Gross <[email protected]>
Cc: "Linux Next Mailing List" <[email protected]>
Link: https://lore.kernel.org/[email protected]
Reported-by: Stephen Rothwell <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Fixes: 91d3902 ("rust: samples: add tracepoint to Rust sample")
Signed-off-by: Miguel Ojeda <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: ojeda

samples/rust/Makefile

@@ -2,6 +2,8 @@
 ccflags-y += -I$(src)				# needed for trace events
 
 obj-$(CONFIG_SAMPLE_RUST_MINIMAL)		+= rust_minimal.o
-obj-$(CONFIG_SAMPLE_RUST_PRINT)			+= rust_print.o rust_print_events.o
+obj-$(CONFIG_SAMPLE_RUST_PRINT)			+= rust_print.o
+
+rust_print-y := rust_print_main.o rust_print_events.o
 
 subdir-$(CONFIG_SAMPLE_RUST_HOSTPROGS)		+= hostprogs