[PATCH v2] docs: rust: quick-start: update Ubuntu instructions

[Igor Korotin <igor.korotin@yahoo.com>]

Ubuntu’s rust-1.80 and bindgen-0.65 packages don't set their tools
as defaults. They should be defined explicitly.

Signed-off-by: Igor Korotin <igor.korotin@yahoo.com>
---

Changes since v1:
 - rewrote commit message to be more concise
 - reworked instruction's steps not to make global changes
 - added overall build command for Ubuntu.
 - https://lore.kernel.org/all/20250331170118.1376899-1-igor.korotin@yahoo.com/
 
 Documentation/rust/quick-start.rst | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/Documentation/rust/quick-start.rst b/Documentation/rust/quick-start.rst
index 4aa50e5fcb8c..3651d726ede0 100644
--- a/Documentation/rust/quick-start.rst
+++ b/Documentation/rust/quick-start.rst
@@ -95,10 +95,25 @@ they should generally work out of the box, e.g.::
 
 	apt install rustc-1.80 rust-1.80-src bindgen-0.65 rustfmt-1.80 rust-1.80-clippy
 
+``PATH`` needs to be set when installing rust 1.80 with apt, e.g.::
+
+	PATH=/usr/lib/rust-1.80/bin:$PATH
+
+Deb package bindgen-0.65 does not set itself as a default, thus it should be set
+explicitly, e.g.::
+
+	BINDGEN=bindgen-0.65
+
 ``RUST_LIB_SRC`` needs to be set when using the versioned packages, e.g.::
 
 	RUST_LIB_SRC=/usr/src/rustc-$(rustc-1.80 --version | cut -d' ' -f2)/library
 
+The overall command should be the following::
+
+	make LLVM=1 PATH=/usr/lib/rust-1.80/bin:$PATH \
+		RUST_LIB_SRC=/usr/src/rustc-$(rustc-1.80 --version | cut -d' ' -f2)/library \
+		BINDGEN=bindgen-0.65 <target>
+
 In addition, ``bindgen-0.65`` is available in newer releases (24.04 LTS and
 24.10), but it may not be available in older ones (20.04 LTS and 22.04 LTS),
 thus ``bindgen`` may need to be built manually (please see below).
-- 
2.43.0