Change incompatible-pointer-types warning to error
-basic_flags := -std=c99 -pipe -Wall -Wpedantic -Wextra -Werror=implicit-function-declaration -Wconversion -D_XOPEN_SOURCE_EXTENDED=1
+basic_flags := -std=c99 -pipe -Wall -Wpedantic -Wextra -Werror=implicit-function-declaration -Werror=incompatible-pointer-types -Wconversion -D_XOPEN_SOURCE_EXTENDED=1
debug_flags := -DDEBUG -ggdb
sanitize_flags := -fsanitize=address -fsanitize=undefined
# note: -fsanitize=leak not available on at least Mac 10.12
