Support for PC platform (#12)

* improvements for cross-platform compiling

* moved tactility-core to libs/

* splitup improvements

* remove git/gitmodules from freertos

* better platformbetter platform checks

* added build scripts

* delete mbedtls

* re-add mbedtls

* fixes and improvements

* added pc build

* simplify build scripts

* revert build scrpit

* updated builds

* fix for pc

* fix for pc

* fix for build

libs/mbedtls/configs/ext/README.md

@@ -0,0 +1,25 @@
+Summary
+-------
+
+The two files:
+
+* crypto_config_profile_medium.h
+* tfm_mbedcrypto_config_profile_medium.h
+
+are copyright The Mbed TLS Contributors, and are distributed under the license normally
+used by Mbed TLS: a dual Apache 2.0 or GPLv2-or-later license.
+
+Background
+----------
+
+The two files crypto_config_profile_medium.h and tfm_mbedcrypto_config_profile_medium.h
+are taken verbatim from the TF-M source code here:
+
+https://git.trustedfirmware.org/TF-M/trusted-firmware-m.git/tree/lib/ext/mbedcrypto/mbedcrypto_config
+
+In TF-M, they are distributed under a 3-Clause BSD license, as noted at the top of the files.
+
+In Mbed TLS, with permission from the TF-M project, they are distributed under a dual [Apache-2.0](https://spdx.org/licenses/Apache-2.0.html) OR [GPL-2.0-or-later](https://spdx.org/licenses/GPL-2.0-or-later.html) license, with copyright assigned to The Mbed TLS Contributors.
+
+We only retain the note at the top of the files because we are taking the files verbatim, for ease of
+maintenance.