Makefile: Disable Make's implict suffix rules

Author: WardBrian

make/compiler_flags

@@ -70,6 +70,13 @@ CXX_VERSION :=  $(shell $(CXX) -dumpfullversion -dumpversion 2>&1)
 CXX_MAJOR := $(word 1,$(subst ., ,$(CXX_VERSION)))
 CXX_MINOR := $(word 2,$(subst ., ,$(CXX_VERSION)))
 
+# disable Make's implicit suffix rules
+# see: https://www.gnu.org/software/make/manual/html_node/Implicit-Rules.html
+# this should make Make slightly faster, as well as avoiding some unexpected
+# behavior when there are other files lying around with the same name as
+# Stan models
+.SUFFIXES:
+
 ################################################################################
 # Set optional compiler flags for performance
 #