Fix typo in endfunction
This MR addresses a warning emitted by cmake during downstream builds:
CMake Warning (dev) in D:/bld/ldas-tools-al_1572273658290/_h_env/Library/share/ldas-tools/cmake/Modules/Autotools/ArchiveX/cx_ldas_prog_cxx.cmake:
A logical block opening on the line
D:/bld/ldas-tools-al_1572273658290/_h_env/Library/share/ldas-tools/cmake/Modules/Autotools/ArchiveX/cx_ldas_prog_cxx.cmake:10 (function)
closes on the line
D:/bld/ldas-tools-al_1572273658290/_h_env/Library/share/ldas-tools/cmake/Modules/Autotools/ArchiveX/cx_ldas_prog_cxx.cmake:26 (endfunction)
with mis-matching arguments.