Explicitly link tests with pthreads

Required to use pthreads within tests.

Signed-off-by: Paul Elliott <paul.elliott@arm.com>

tests/CMakeLists.txt

@@ -1,5 +1,8 @@
+find_package(Threads)
+
 set(libs
     ${mbedtls_target}
+    ${CMAKE_THREAD_LIBS_INIT}
 )
 
 # Set the project root directory if it's not already defined, as may happen if

tests/Makefile

@@ -57,6 +57,7 @@ else
 DLEXT ?= so
 EXEXT=
 SHARED_SUFFIX=
+LOCAL_LDFLAGS += -lpthread
 endif
 
 ifdef WINDOWS