archivers/libdeflate: update the port to version 1.15

- The build system had been switched to CMake, adjust the Makefile
  accordingly and convert outgrown PLIST_FILES into static pkg-plist
- Backport one upstream commit for the sake of consistency, so unit
  tests reflect on release binaries (it also happens to inadvertently
  inhibit detection of futimes(2), which is deprecated interface as
  it does not provide nanosecond accuracy, so it's probably okay)
- Do not pass "-O2 -DNDEBUG" on release CFLAGS: -O2 is redundant and
  NDEBUG is not actually used anywhere in the library source code

PR:	268519