common.mk: Set WHICH to command -v

defs.mk derives WHICH from the external which binary, first from a
hardcoded /usr/bin/which path and then with a `which which` fallback, while
the probes for time, ruff, pyright, and python3 call which directly.
Systems that do not ship the which package, such as minimal containers, are
left to the shell's PATH search.

Define WHICH once in common.mk as the POSIX command -v builtin and drop the
old definition from defs.mk. Route the remaining direct which calls through
$(WHICH):

- projects-dir.mk: TIME probe
- py-check.mk: PY_CHECK_RUFF and PY_CHECK_PYRIGHT probes
- py-version.mk: PYTHON lookup

command -v runs in the /bin/sh that $(shell) already uses, so the build no
longer depends on the which package. The builtin names that command -v
reports for echo, test, pwd, and printf are safe, because every use of
those variables runs through the shell, and the bash time keyword keeps the
-p output format identical to the GNU time binary.

Assisted-by: unsloth/Qwen3.8-27B-GGUF:Q4_K_M with pi.dev v1.3.0
Signed-off-by: Jan Lindemann <jan@janware.com>

make/common.mk

@@ -7,6 +7,9 @@ COMMON_MK_INCLUDED           = true
 
 Q                           ?= @
 INTERACTIVE                 ?= auto
+ifndef WHICH
+  WHICH                     := command -v
+endif
 BROWSER                     ?= xdg-open
 JWB_SCRIPT_DIR              ?= $(firstword $(wildcard $(JWBDIR)/scripts $(JWBDIR)/bin) jwb-script-dir-not-found)
 

make/defs.mk

@@ -11,9 +11,6 @@ include $(JWBDIR)/make/projects.mk
 
 # ----- Executables
 
-ifndef WHICH
-  WHICH                     := $(firstword $(wildcard /usr/bin/which) $(shell which which))
-endif
 ifndef GREP
   GREP                      := $(shell $(WHICH) grep)
 endif

make/projects-dir.mk

@@ -115,7 +115,7 @@ endif
 
 EDITOR                      ?= xdg-open
 ifeq ($(TIME),)
-  TIME                      := $(shell which time)
+  TIME                      := $(shell $(WHICH) time)
   ifneq ($(TIME),)
     TIME                    += -p
   endif

make/py-check.mk

@@ -23,7 +23,7 @@ ifndef PY_CHECK_MYPY
 endif
 
 ifndef PY_CHECK_RUFF
-  PY_CHECK_RUFF             := $(shell which ruff 2>/dev/null)
+  PY_CHECK_RUFF             := $(shell $(WHICH) ruff 2>/dev/null)
   ifneq ($(PY_CHECK_RUFF),)
     PY_CHECK_RUFF           += --config $(TOPDIR)/pyproject.toml
   endif
@@ -38,7 +38,7 @@ ifndef PY_CHECK_YAPF
 endif
 
 ifndef PY_CHECK_PYRIGHT
-  PY_CHECK_PYRIGHT          := $(shell which pyright 2>/dev/null)
+  PY_CHECK_PYRIGHT          := $(shell $(WHICH) pyright 2>/dev/null)
   TD_GENERATE_FILES         += pyrightconfig.json
 endif
 

make/py-version.mk

@@ -6,7 +6,7 @@ ifneq ($(PYTHON_VERSION),)
 else
   ifeq ($(PYTHON),)
     #PYTHON                  := $(lastword $(shell /bin/bash -O extglob -c "ls -v /usr/bin/python[0-9].+([0-9])"))
-    PYTHON                  := $(shell which python3 | xargs readlink -f)
+    PYTHON                  := $(shell $(WHICH) python3 | xargs readlink -f)
   endif
   PYTHON_VERSION            ?= $(patsubst python%,%,$(notdir $(PYTHON)))
 endif