Temporarily disable use of TinyCrypt with Mbed-OS

TinyCrypt uses a modified version of micro-ecc that is also used by the Mbed Cordio BLE stack. When building mcuboot for a target with BLE enabled, this causes multiple-defined symbol errors during linking. Due to the nature of Mbed's current build system, it is difficult to fix this.

Mbed will soon release a more flexible cmake-based build system that will make it possible to exclude these TinyCrypt files from an application build that may also link Cordio BLE sources.

Until then, this commit temporarily disables the use of TinyCrypt with Mbed-OS and excludes its sources from the build to avoid this build error.

Signed-off-by: George Beckstein <becksteing@embeddedplanet.com>

Author: AGlass0fMilk

.mbedignore

@@ -14,4 +14,6 @@ ext/fiat/*
 ext/mbedtls/*
 ext/mbedtls-asn1/*
 ext/nrf/*
-ext/tinycrypt/tests/*
+ext/tinycrypt/tests/*
+ext/tinycrypt/*
+ext/tinycrypt-sha512/*

boot/mbed/include/mcuboot_config/mcuboot_config.h

@@ -46,12 +46,10 @@
 #define MCUBOOT_USE_MBED_TLS
 #elif (MCUBOOT_CRYPTO_BACKEND == TINYCRYPT)
 /**
- * XXX TinyCrypt is currently only supported in GCC builds
- * See https://github.com/mcu-tools/mcuboot/pull/791#discussion_r515050672 for more information.
+ * XXX TinyCrypt is currently not supported by Mbed-OS due to build conflicts.
+ * See https://github.com/AGlass0fMilk/mbed-mcuboot-blinky/issues/2
  */
-#if !defined(__GNUC__)
-#error TinyCrypt is currently only supported in GCC builds for Mbed-OS.
-#endif
+#error TinyCrypt is currently not supported by Mbed-OS due to build conflicts.
 #define MCUBOOT_USE_TINYCRYPT
 #endif