The script combine.sh creates an amalgamated C++ source file that can be used with or without basisu_transcoder.h. This isn't a header-only file but it does offer a similar level of simplicity when integrating into a project.
Create basisutranslib.cpp from the transcoder source using:
cd basis_universal/contrib/single_file_transcoder ./combine.sh -r ../../transcoder -o basisutranslib.cpp basisutranslib-in.cpp
Then add the resulting file to your project (see the example files).
If certain features will never_ be enabled, e.g. BASISD_SUPPORT_BC7_MODE6_OPAQUE_ONLY, then combine.sh can be told to exclude files completely:
./combine.sh -r ../../transcoder -x basisu_transcoder_tables_bc7_m6.inc -o basisutranslib.cpp basisutranslib-in.cpp
Excluding the BC7 mode 6 support reduces the generated source by 1.2MB, which is the choice taken in both basisutranslib-in.cpp and create_translib.sh, will run the above script, creating the final basisutranslib.cpp.
Note: the amalgamation script will run on pretty much anything but is extremely slow on Windows with the bash included with Git.
Because all it now takes to support Basis Universal is the addition of a single file, two if using the header, with no configuration or further build steps (the out-of-the-box defaults tailor the included formats for various platforms).
The library is small, adding, for example, around 250kB to an Emscripten compiled WebAssembly project (with transcoding disabled for BC7 and ATC; disabling ASTC will remove a further 64kB, and gzip will approximately half the wasm file).