feat(unittests): add a unit test framework.

This patch adds all the infrastructure needed to run unit tests for
RMM, including a new variant for platform host, called `host_test`.

To build and run the tests:

cmake -DRMM_CONFIG=host_defcfg -DHOST_VARIANT=host_test \
  -DCMAKE_BUILD_TYPE=Debug -S ${RMM_SOURCE_DIR} -B ${RMM_BUILD_DIR}
cmake --build ${RMM_BUILD_DIR} -- run-unittests

Signed-off-by: Javier Almansa Sobrino <javier.almansasobrino@arm.com>
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
Change-Id: If16686e111d91c563f8e7281d4ee7ca2864125ae
diff --git a/toolchains/fake_host/gnu.cmake b/toolchains/fake_host/gnu.cmake
index ca2f48f..70a1c34 100644
--- a/toolchains/fake_host/gnu.cmake
+++ b/toolchains/fake_host/gnu.cmake
@@ -12,6 +12,14 @@
     DOC "Path to gcc."
     REQUIRED)
 
+#
+# Needed to build CppUTest for unit tests
+#
+find_program(CMAKE_CXX_COMPILER
+    NAMES "g++"
+    DOC "Path to g++."
+    REQUIRED)
+
 set(CMAKE_ASM_COMPILER ${CMAKE_C_COMPILER})
 
 string(APPEND CMAKE_EXE_LINKER_FLAGS_INIT "-Wl,--build-id=none ")