Makefile and use of $$
Make needs to distinguish whether you want a $ to use as introducing a make-variable reference, such as ${FOOBAR} or as a plain $ passed on to the shell. The make specification (Section Macros) says that to do the latter, you must use $$ which is replaced by a single $ and passed to the shell. In effect, your snippet reads as
for file_exe in `find . -name "zip_exe-*"`; do \ ./${file_exe} -d some/unzip/path/lib; \doneto the shell.
Style note: Iterating over file lists created by backticks is considered bad style, since it may overflow the ARG_MAX limit. Better to read the file names one-by-one with
find . -name "zip_exe-*" | \while read -r file_exe; do \ ./${file_exe} -d some/unzip/path/lib; \done