eclass/tests: Add a minimal benchmark for cargo.eclass

The initial results on my machine are:

```
real  252 it/s
user  289 it/s
```

Signed-off-by: Michał Górny <mgorny@gentoo.org>

1 files changed, 107 insertions, 0 deletions

diff --git a/eclass/tests/cargo-bench.sh b/eclass/tests/cargo-bench.sh
new file mode 100755
index 000000000000..cdc5e4431c14
--- /dev/null
+++ b/eclass/tests/cargo-bench.sh
@@ -0,0 +1,107 @@
+#!/bin/bash
+# Copyright 2023 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+source tests-common.sh || exit
+
+export LC_ALL=C
+
+ITERATIONS=1000
+RUNS=3
+
+doit() {
+	for (( i = 0; i < ITERATIONS; i++ )); do
+		SRC_URI="
+			$(cargo_crate_uris)
+		"
+	done
+}
+
+timeit() {
+	local real=()
+	local user=()
+	local x vr avg
+
+	for (( x = 0; x < RUNS; x++ )); do
+		while read tt tv; do
+			case ${tt} in
+				real) real+=( ${tv} );;
+				user) user+=( ${tv} );;
+			esac
+		done < <( ( time -p doit ) 2>&1 )
+	done
+
+	[[ ${#real[@]} == ${RUNS} ]] || die "Did not get ${RUNS} real times"
+	[[ ${#user[@]} == ${RUNS} ]] || die "Did not get ${RUNS} user times"
+
+	local xr avg
+	for x in real user; do
+		xr="${x}[*]"
+		avg=$(dc -S 3 -e "${ITERATIONS} ${RUNS} * ${!xr} + + / p")
+
+		printf '%s %4.0f it/s\n' "${x}" "${avg}"
+	done
+}
+
+# taken from cryptograpy-41.0.1
+CRATES="
+	Inflector-0.11.4
+	aliasable-0.1.3
+	asn1-0.15.2
+	asn1_derive-0.15.2
+	autocfg-1.1.0
+	base64-0.13.1
+	bitflags-1.3.2
+	cc-1.0.79
+	cfg-if-1.0.0
+	foreign-types-0.3.2
+	foreign-types-shared-0.1.1
+	indoc-1.0.9
+	libc-0.2.144
+	lock_api-0.4.9
+	memoffset-0.8.0
+	once_cell-1.17.2
+	openssl-0.10.54
+	openssl-macros-0.1.1
+	openssl-sys-0.9.88
+	ouroboros-0.15.6
+	ouroboros_macro-0.15.6
+	parking_lot-0.12.1
+	parking_lot_core-0.9.7
+	pem-1.1.1
+	pkg-config-0.3.27
+	proc-macro-error-1.0.4
+	proc-macro-error-attr-1.0.4
+	proc-macro2-1.0.59
+	pyo3-0.18.3
+	pyo3-build-config-0.18.3
+	pyo3-ffi-0.18.3
+	pyo3-macros-0.18.3
+	pyo3-macros-backend-0.18.3
+	quote-1.0.28
+	redox_syscall-0.2.16
+	scopeguard-1.1.0
+	smallvec-1.10.0
+	syn-1.0.109
+	syn-2.0.18
+	target-lexicon-0.12.7
+	unicode-ident-1.0.9
+	unindent-0.1.11
+	vcpkg-0.2.15
+	version_check-0.9.4
+	windows-sys-0.45.0
+	windows-targets-0.42.2
+	windows_aarch64_gnullvm-0.42.2
+	windows_aarch64_msvc-0.42.2
+	windows_i686_gnu-0.42.2
+	windows_i686_msvc-0.42.2
+	windows_x86_64_gnu-0.42.2
+	windows_x86_64_gnullvm-0.42.2
+	windows_x86_64_msvc-0.42.2
+"
+
+inherit cargo
+timeit
+
+texit