build(Makefile): add per-target timing via SHELL wrapper (#22862)

pre-commit and pre-push only reported total elapsed time at the end,
making it hard to identify which jobs are slow.

Add a `MAKE_TIMED=1` mode that replaces `SHELL` with a wrapper
(`scripts/lib/timed-shell.sh`) to print wall-clock time for each
recipe. pre-commit and pre-push enable this on their sub-makes.

Ad-hoc use: `make MAKE_TIMED=1 test`

Makefile

@@ -19,6 +19,16 @@ SHELL := bash
 .SHELLFLAGS := -ceu
 .ONESHELL:
 
+# When MAKE_TIMED=1, replace SHELL with a wrapper that prints
+# elapsed wall-clock time for each recipe. pre-commit and pre-push
+# set this on their sub-makes so every parallel job reports its
+# duration. Ad-hoc usage: make MAKE_TIMED=1 test
+ifdef MAKE_TIMED
+SHELL := $(CURDIR)/scripts/lib/timed-shell.sh
+.SHELLFLAGS = $@ -ceu
+export MAKE_TIMED
+endif
+
 # This doesn't work on directories.
 # See https://stackoverflow.com/questions/25752543/make-delete-on-error-for-directory-targets
 .DELETE_ON_ERROR:
@@ -753,10 +763,10 @@ endef
 pre-commit:
 	start=$$(date +%s)
 	echo "=== Phase 1/2: gen + fmt ==="
-	$(MAKE) -j$(PARALLEL_JOBS) --output-sync=target gen fmt
+	$(MAKE) -j$(PARALLEL_JOBS) --output-sync=target MAKE_TIMED=1 gen fmt
 	$(check-unstaged)
 	echo "=== Phase 2/2: lint + build ==="
-	$(MAKE) -j$(PARALLEL_JOBS) --output-sync=target \
+	$(MAKE) -j$(PARALLEL_JOBS) --output-sync=target MAKE_TIMED=1 \
 		lint \
 		lint/typos \
 		build/coder-slim_$(GOOS)_$(GOARCH)$(GOOS_BIN_EXT)
@@ -767,10 +777,10 @@ pre-commit:
 pre-push:
 	start=$$(date +%s)
 	echo "=== Phase 1/2: gen + fmt + postgres ==="
-	$(MAKE) -j$(PARALLEL_JOBS) --output-sync=target gen fmt test-postgres-docker
+	$(MAKE) -j$(PARALLEL_JOBS) --output-sync=target MAKE_TIMED=1 gen fmt test-postgres-docker
 	$(check-unstaged)
 	echo "=== Phase 2/2: lint + build + test ==="
-	$(MAKE) -j$(PARALLEL_JOBS) --output-sync=target \
+	$(MAKE) -j$(PARALLEL_JOBS) --output-sync=target MAKE_TIMED=1 \
 		lint \
 		lint/typos \
 		build/coder-slim_$(GOOS)_$(GOARCH)$(GOOS_BIN_EXT) \

scripts/lib/timed-shell.sh

@@ -0,0 +1,41 @@
+#!/usr/bin/env bash
+# timed-shell.sh wraps bash with per-target wall-clock timing.
+#
+# Recipe invocation:    timed-shell.sh <target> -ceu <recipe>
+# $(shell ...) calls:   timed-shell.sh -c <command>
+#
+# Enable via Makefile:
+#   SHELL := $(CURDIR)/scripts/lib/timed-shell.sh
+#   .SHELLFLAGS = $@ -ceu
+#
+# $(shell ...) uses SHELL but passes -c directly, not .SHELLFLAGS.
+# Detect this and delegate to bash without timing output.
+if [[ $1 == -* ]]; then
+	exec bash "$@"
+fi
+
+set -eu
+
+target=$1
+shift
+
+bold=$(tput bold 2>/dev/null) || true
+green=$(tput setaf 2 2>/dev/null) || true
+red=$(tput setaf 1 2>/dev/null) || true
+reset=$(tput sgr0 2>/dev/null) || true
+
+start=$(date +%s)
+echo "${bold}==> ${target}${reset}"
+
+set +e
+bash "$@"
+rc=$?
+set -e
+
+elapsed=$(($(date +%s) - start))
+if ((rc == 0)); then
+	echo "${bold}${green}==> ${target} completed in ${elapsed}s${reset}"
+else
+	echo "${bold}${red}==> ${target} FAILED after ${elapsed}s${reset}" >&2
+	exit $rc
+fi