use command -v instead which command

Minimize build requirement.
Use standard POSIX sh `command -v` instead separated external which command.

Fixes ostreedev#2825

Signed-off-by: Tomasz Kłoczko <kloczek@github.com>

tests/libtest.sh

@@ -107,7 +107,7 @@ export TEST_GPG_KEYHOME=${test_tmpdir}/gpghome
 export OSTREE_GPG_HOME=${test_tmpdir}/gpghome/trusted
 
 assert_has_setfattr() {
-    if ! which setfattr 2>/dev/null; then
+    if ! command -v setfattr 2>/dev/null; then
         fatal "no setfattr available to determine xattr support"
     fi
 }
@@ -725,9 +725,9 @@ which_gpg () {
     local opt
 
     # Prefer gpg2 in case gpg refers to gpg1
-    if which gpg2 &>/dev/null; then
+    if command -v gpg2 &>/dev/null; then
         gpg=gpg2
-    elif which gpg &>/dev/null; then
+    elif command -v gpg &>/dev/null; then
         gpg=gpg
     else
         # Succeed but don't return anything.

tests/test-delta-ed25519.sh

@@ -34,7 +34,7 @@ ostree_repo_init repo --mode=archive
 
 mkdir files
 for bin in ${bindatafiles}; do
-    cp $(which ${bin}) files
+    cp $(command -v ${bin}) files
 done
 
 ${CMD_PREFIX} ostree --repo=repo commit -b test -s test --tree=dir=files

tests/test-delta-sign.sh

@@ -35,7 +35,7 @@ ostree_repo_init repo --mode=archive
 
 mkdir files
 for bin in ${bindatafiles}; do
-    cp $(which ${bin}) files
+    cp $(command -v ${bin}) files
 done
 
 ${CMD_PREFIX} ostree --repo=repo commit -b test -s test --tree=dir=files

tests/test-delta.sh

@@ -33,7 +33,7 @@ ostree_repo_init repo --mode=archive
 
 mkdir files
 for bin in ${bindatafiles}; do
-    cp $(which ${bin}) files
+    cp $(command -v ${bin}) files
 done
 
 ${CMD_PREFIX} ostree --repo=repo commit -b test -s test --tree=dir=files