build(Makefile): Add /bin/bash

Author: tony

Makefile

@@ -1,5 +1,6 @@
 PY_FILES= find . -type f -not -path '*/\.*' | grep -i '.*[.]py$$' 2> /dev/null
 DOC_FILES= find . -type f -not -path '*/\.*' | grep -i '.*[.]rst\$\|.*[.]md\$\|.*[.]css\$\|.*[.]py\$\|mkdocs\.yml\|CHANGES\|TODO\|.*conf\.py' 2> /dev/null
+SHELL := /bin/bash
 
 
 entr_warn: