CMake: use debug build when cross-compiling

This is a quick & dirty fix assuming that when cross-compiling,
we do that with intention to debug.

It'd be much better to detect user wants a debug build from `./configure`
arguments but this is left for later.

closed/OpenJ9.gmk

@@ -407,6 +407,13 @@ ifeq (true,$(OPENJ9_ENABLE_CMAKE))
     endif
   endif # windows
 
+  # Temporary hack for development...
+  ifneq ($(OPENJDK_BUILD_CPU),$(OPENJDK_TARGET_CPU))
+    CMAKE_ARGS += \
+      -DCMAKE_BUILD_TYPE=Debug \
+      -DCMAKE_EXPORT_COMPILE_COMMANDS=ON
+  endif
+
   ifneq (,$(CCACHE))
     # openjdk makefiles add a bunch of environemnt variables to the ccache command.
     # CMake will not parse this properly, so we wrap the whole thing in the env command.