Build: Add optional install.cmake for platform

Change-Id: I04a935be89964e7c2d3b9fd442d10e4b92baf560
Signed-off-by: Roman Mazurak <Roman.Mazurak@infineon.com>
Signed-off-by: Chris Brand <chris.brand@cypress.com>
diff --git a/config/check_config.cmake b/config/check_config.cmake
index ef64080..f4360cf 100644
--- a/config/check_config.cmake
+++ b/config/check_config.cmake
@@ -127,3 +127,9 @@
 ###################### Compiler check for FP support ###########################
 
 include(config/cp_check.cmake)
+
+###################### Platform-specific checks ################################
+
+if (EXISTS ${CMAKE_SOURCE_DIR}/platform/ext/target/${TFM_PLATFORM}/check_config.cmake)
+    include(platform/ext/target/${TFM_PLATFORM}/check_config.cmake)
+endif()