https://github.com/OpenTTD/OpenSFX/pull/49
--- a/Makefile
+++ b/Makefile
@@ -98,7 +98,7 @@ all: $(GENERATE_GRF) $(GENERATE_DOC) bundle_tar
 MAKE           ?= make
 MAKE_FLAGS     ?= -r
 
-NML            ?= $(shell which nmlc 2>/dev/null)
+NML            ?= $(shell command -v nmlc 2>/dev/null)
 NML_FLAGS      ?= -c
 ifdef REQUIRED_NML_BRANCH
 	NML_BRANCH = $(shell nmlc --version | head -n1 | cut -d. -f1-2)
@@ -108,7 +108,7 @@ ifdef MIN_NML_REVISION
 endif
 
 ifdef MAIN_SRC_FILE
-	CC             ?= $(shell which gcc 2>/dev/null)
+	CC             ?= $(shell command -v gcc 2>/dev/null)
 	CC_FLAGS       ?= -C -E -nostdinc -x c-header
 endif
 
@@ -116,11 +116,11 @@ AWK            ?= awk
 
 GREP           ?= grep
 
-GIT            ?= $(shell git status >/dev/null 2>/dev/null && which git 2>/dev/null)
+GIT            ?= $(shell git status >/dev/null 2>/dev/null && command -v git 2>/dev/null)
 
 PYTHON         ?= python
 
-UNIX2DOS       ?= $(shell which unix2dos 2>/dev/null)
+UNIX2DOS       ?= $(shell command -v unix2dos 2>/dev/null)
 UNIX2DOS_FLAGS ?= $(shell [ -n $(UNIX2DOS) ] && $(UNIX2DOS) -q --version 1>&2 2>/dev/null && echo "-q" || echo "")
 
 ################################################################
@@ -191,7 +191,7 @@ ifdef GFX_SCRIPT_LIST_FILES
 # include dependency file, if we generate graphics
 -include Makefile_gfx.dep
 
-GIMP           ?= $(shell [ `which gimp 2>/dev/null` ] && echo "gimp" || echo "")
+GIMP           ?= $(shell [ `command -v gimp 2>/dev/null` ] && echo "gimp" || echo "")
 GIMP_FLAGS     ?= -n -i -b - <
 
 %.scm: $(SCRIPT_DIR)/gimpscript $(SCRIPT_DIR)/gimp.sed
@@ -309,26 +309,26 @@ clean::
 # and the distribution bundles like bundle_tar, bundle_zip, ...
 
 # Programme definitions
-TAR            ?= $(shell which tar 2>/dev/null)
+TAR            ?= $(shell command -v tar 2>/dev/null)
 TAR_FLAGS      ?= -cf
 
-ZIP            ?= $(shell which zip 2>/dev/null)
+ZIP            ?= $(shell command -v zip 2>/dev/null)
 ZIP_FLAGS      ?= -9rq
 
-GZIP           ?= $(shell which gzip 2>/dev/null)
+GZIP           ?= $(shell command -v gzip 2>/dev/null)
 GZIP_FLAGS     ?= -9f
 
-BZIP           ?= $(shell which bzip2 2>/dev/null)
+BZIP           ?= $(shell command -v bzip2 2>/dev/null)
 BZIP_FLAGS     ?= -9fk
 
-XZ             ?= $(shell which xz 2>/dev/null)
+XZ             ?= $(shell command -v xz 2>/dev/null)
 XZ_FLAGS       ?= -efk
 
 # OSX has nice extended file attributes which create their own file within tars. We don't want those, thus don't copy them
 CP_FLAGS       ?= $(shell [ "$(OSTYPE)" = "Darwin" ] && echo "-rfX" || echo "-rf")
 
 # Use the grfID programme to find the checksum which OpenTTD checks
-GRFID          ?= $(shell which grfid 2>/dev/null)
+GRFID          ?= $(shell command -v grfid 2>/dev/null)
 GRFID_FLAGS    ?= -m
 
 # Rules on how to generate filenames. Usually no need to change
@@ -484,7 +484,7 @@ endif
 ifeq ($(shell echo "$(OSTYPE)" | cut -d_ -f1),MINGW32)
 # If CC has been set to the default implicit value (cc), check if it can be used. Otherwise use a saner default.
 ifeq "$(origin CC)" "default"
-	CC=$(shell which cc 2>/dev/null && echo "cc" || echo "gcc")
+	CC=$(shell command -v cc 2>/dev/null && echo "cc" || echo "gcc")
 endif
 WIN_VER = $(shell echo "$(OSTYPE)" | cut -d- -f2 | cut -d. -f1)
 ifeq ($(WIN_VER),5)
--- a/Makefile.in
+++ b/Makefile.in
@@ -9,7 +9,7 @@
 		> $@
 	$(_V) [ -z "$(UNIX2DOS)" ] || $(UNIX2DOS) $(UNIX2DOS_FLAGS) $@
 
-MD5SUM         ?= $(shell which md5sum 2>/dev/null)
+MD5SUM         ?= $(shell command -v md5sum 2>/dev/null)
 
 $(SOUND_FILE): $(SRC_DIR)/$(BASE_FILENAME).sfo $(SOUND_FILES) Makefile Makefile.in Makefile.config
 # replace the place holders for version and name by the respective variables:
@@ -18,7 +18,7 @@ $(SOUND_FILE): $(SRC_DIR)/$(BASE_FILENAME).sfo $(SOUND_FILES) Makefile Makefile.
 	$(_V) $(CATCODEC) $(CATCODEC_FLAGS) $(SRC_DIR)/$@
 	$(_V) cp $(SRC_DIR)/$@ .
 
-ifneq ("$(shell which $(MD5SUM) 2>/dev/null)","")
+ifneq ("$(shell command -v $(MD5SUM) 2>/dev/null)","")
 $(OBS_FILE): $(SOUND_FILE) $(LANG_FILES) Makefile Makefile.in Makefile.config
 	$(_E) "[Generating:] $@"
 	@echo "[metadata]" > $@
--- a/Makefile.local.sample
+++ b/Makefile.local.sample
@@ -57,7 +57,7 @@
 # UNIX2DOS_FLAGS = -q
 # NML_FLAGS      =
 
-# NFORENUM       = $(shell [ `which nforenum 2>/dev/null` ] && echo "nforenum" || echo "renum")
+# NFORENUM       = $(shell [ `command -v nforenum 2>/dev/null` ] && echo "nforenum" || echo "renum")
 # GRFCODEC       = grfcodec
 # TAR            = tar
 # ZIP            = zip
@@ -67,7 +67,7 @@
 # AWK            = awk
 # GIT            = git
 # MAKE           = make
-# UNIX2DOS       = $(shell [ `which unix2dos 2>/dev/null` ] && echo "unix2dos" || echo "")
+# UNIX2DOS       = $(shell [ `command -v unix2dos 2>/dev/null` ] && echo "unix2dos" || echo "")
 # MD5SUM         = $(shell [ "$(OSTYPE)" = "Darwin" ] && echo "md5 -r" || echo "md5sum")
 # NML            = nml.py
 
--- a/scripts/Makefile.def
+++ b/scripts/Makefile.def
@@ -24,7 +24,7 @@ NML_FLAGS      ?=
 CP_FLAGS       ?= $(shell [ "$(OSTYPE)" = "Darwin" ] && echo "-rfX" || echo "-rf")
 
 
-NFORENUM       ?= $(shell [ `which nforenum 2>/dev/null` ] && echo "nforenum" || echo "renum")
+NFORENUM       ?= $(shell [ `command -v nforenum 2>/dev/null` ] && echo "nforenum" || echo "renum")
 GRFCODEC       ?= grfcodec
 CATCODEC       ?= catcodec
 TAR            ?= tar
@@ -35,7 +35,7 @@ CC             ?= gcc
 AWK            ?= awk
 GIT            ?= git
 MAKE           ?= make
-UNIX2DOS       ?= $(shell [ `which unix2dos 2>/dev/null` ] && echo "unix2dos" || echo "")
+UNIX2DOS       ?= $(shell [ `command -v unix2dos 2>/dev/null` ] && echo "unix2dos" || echo "")
 # Macs have a different md5 command than linux or mingw envirnoment:
 MD5SUM         ?= $(shell [ "$(OSTYPE)" = "Darwin" ] && echo "md5 -r" || echo "md5sum")
 NML            ?= nml2nfo