Do not rely on which to be present in the system

For portability, it is better to use the built-in `command` to check the
existance of executables in the system.

doc/manual/make-tempfiles.sh

@@ -27,7 +27,7 @@ then
         SBCL_HOME=$SBCL_PWD/../../obj/sbcl-home/; export SBCL_HOME
         SBCL_BUILDING_CONTRIB="please asdf install your hook"; export SBCL_BUILDING_CONTRIB
     else
-        SBCLRUNTIME="`which sbcl`"
+        SBCLRUNTIME="`command -v sbcl`"
     fi
 else
     SBCLRUNTIME="$1"

find-gnumake.sh

@@ -8,10 +8,10 @@ find_gnumake() {
     GNUMAKE="$GNUMAKE"
   elif [ "GNU Make" = "`make -v 2>/dev/null | head -n 1 | cut -b 1-8`" ]; then
     GNUMAKE=make
-  elif [ -x "`which gmake`" ] ; then
+  elif [ -x "`command -v gmake`" ] ; then
     # "gmake" is the preferred name in *BSD.
     GNUMAKE=gmake
-  elif [ -x "`which gnumake`" ] ; then
+  elif [ -x "`command -v gnumake`" ] ; then
     # MacOS X aka Darwin
     GNUMAKE=gnumake
   else

generate-version.sh

@@ -2,7 +2,7 @@
 
 git_available_p() {
     # Check that (1) we have git (2) this is a git tree.
-    if ( which git >/dev/null 2>/dev/null && git describe >/dev/null 2>/dev/null )
+    if ( command -v git >/dev/null && git describe >/dev/null 2>/dev/null )
     then
         echo "ok"
     else

make-target-contrib.sh

@@ -22,7 +22,7 @@ LC_ALL=C
 # Just doing CC=${CC:-cc} may be enough, but it needs to be checked
 # that cc is available on all platforms.
 if [ -z $CC ]; then
-    if [ -x "`which cc`" ]; then
+    if [ -x "`command -v cc`" ]; then
         CC=cc
     else
         CC=gcc

tests/run-compiler.sh

@@ -3,7 +3,7 @@
 platform="${SBCL_SOFTWARE_TYPE}-${SBCL_MACHINE_TYPE}"
 
 if [ -z $CC ]; then
-    if [ -x "`which cc`" ]; then
+    if [ -x "`command -v cc`" ]; then
         CC=cc
     else
         CC=gcc