BuildSystem: Download correct cmake if it is not available

script/build.sh

@@ -6,6 +6,11 @@ source $BANAN_SCRIPT_DIR/config.sh
 
 FAKEROOT_FILE="$BANAN_BUILD_DIR/fakeroot-context"
 
+if [[ -z $CMAKE_COMMAND ]]; then
+	echo "No usable cmake binary found" >&2
+	exit 1
+fi
+
 run_fakeroot() {
 	fakeroot -i $FAKEROOT_FILE -s $FAKEROOT_FILE -- /bin/bash -c '$@' bash $@
 }
@@ -66,10 +71,6 @@ if [[ $# -eq 0 ]]; then
 	exit 1
 fi
 
-if [[ -z $CMAKE_COMMAND ]]; then
-	export CMAKE_COMMAND=cmake
-fi
-
 case $1 in
 	toolchain)
 		build_toolchain