Build: Switch mbedtls auto-patching to git am

To avoid occasional CRLF issues with certain windows git config

Change-Id: I97529d1724ecb75e1bf9d50872e513cd3c502ff2
Signed-off-by: Raef Coles <raef.coles@arm.com>
diff --git a/lib/ext/mbedcrypto/CMakeLists.txt b/lib/ext/mbedcrypto/CMakeLists.txt
index 79adce1..7a28ef5 100644
--- a/lib/ext/mbedcrypto/CMakeLists.txt
+++ b/lib/ext/mbedcrypto/CMakeLists.txt
@@ -24,7 +24,7 @@
             GIT_SHALLOW TRUE
             GIT_PROGRESS TRUE
             GIT_SUBMODULES ""
-            PATCH_COMMAND ${GIT_EXECUTABLE} apply ${PATCH_FILES}
+            PATCH_COMMAND ${GIT_EXECUTABLE} am ${PATCH_FILES}
         )
     else()
         FetchContent_Declare(mbedcrypto