There're couple of issues with the code import:

1. Files have mix of proper (LF) and improper (CRLF) line-endings. This makes it hard to work with the sources under Unix. Yes, that's how it was in original Tensilica stuff, but everyone knows that vendor code sucks, and real open source makes it better, even by fixing broken line-endings.
2. (Single) commit message claims it's code from Tensilica/Cadence RC-2010.1 release. But that's clearly not true. Their code did not contain autoconf stuff and claims of copyright by "The ESP8266 Community".

Compilation on OSX returns error:
"xtensa-lx106-elf-ranlib: libhal.a: Error reading windowspill_asm.o: File truncated"
This is due to fact that src/Makefile.am use hardcoded "awk" command instead to autoconf detected $(AWK)

Not sure if this is a problem in error/warning handling in .configuration, automake or make file, but during installation, it exists while writing to PATH if PATH previously added contains folders names with brackets (). This is true for WSL as windows directories contains (x86) and added to PATH

FYI, this repo is included as a submodule in a repo which tries to automate (while still staying human-friendly) complete SDK setup building: https://github.com/pfalcon/esp-open-sdk

It would be still nice to resolve issues raised in #1.

Why it's needed at all? So complicated to compile a handful of files?

$ automake --add-missing
configure.ac:9: error: required directory ./build-aux does not exist
configure.ac:19: error: installing 'build-aux/compile'; error while making link: No such file or directory
configure.ac:14: error: installing 'build-aux/config.guess'; error while making link: No such file or directory
configure.ac:14: error: installing 'build-aux/config.sub'; error while making link: No such file or directory
configure.ac:10: error: installing 'build-aux/install-sh'; error while making link: No such file or directory
configure.ac:10: error: installing 'build-aux/missing'; error while making link: No such file or directory
configure.ac:12: error: required file 'src/config.h.in' not found
src/Makefile.am: error: installing 'build-aux/depcomp'; error while making link: No such file or directory

After mkdir build-aux:

configure.ac:12: error: required file 'src/config.h.in' not found

Building this on Mac results in a "malformed archive" error because the system ar tool is used instead of xtensa-lx106-elf-ar.