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/freertos-kernel/portable/GCC/RISC-V/readme.txt

@@ -0,0 +1,23 @@
+/*
+ * The FreeRTOS kernel's RISC-V port is split between the the code that is
+ * common across all currently supported RISC-V chips (implementations of the
+ * RISC-V ISA), and code that tailors the port to a specific RISC-V chip:
+ *
+ * + FreeRTOS\Source\portable\GCC\RISC-V-RV32\portASM.S contains the code that
+ *   is common to all currently supported RISC-V chips.  There is only one
+ *   portASM.S file because the same file is built for all RISC-V target chips.
+ *
+ * + Header files called freertos_risc_v_chip_specific_extensions.h contain the
+ *   code that tailors the FreeRTOS kernel's RISC-V port to a specific RISC-V
+ *   chip.  There are multiple freertos_risc_v_chip_specific_extensions.h files
+ *   as there are multiple RISC-V chip implementations.
+ *
+ * !!!NOTE!!!
+ * TAKE CARE TO INCLUDE THE CORRECT freertos_risc_v_chip_specific_extensions.h
+ * HEADER FILE FOR THE CHIP IN USE.  This is done using the assembler's (not the
+ * compiler's!) include path.  For example, if the chip in use includes a core
+ * local interrupter (CLINT) and does not include any chip specific register
+ * extensions then add the path below to the assembler's include path:
+ * FreeRTOS\Source\portable\GCC\RISC-V-RV32\chip_specific_extensions\RV32I_CLINT_no_extensions
+ *
+ */