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

@@ -366,7 +366,9 @@ ifeq (true,$(OPENJ9_ENABLE_CMAKE))
       CMAKE_ARGS += \
         -DCMAKE_TOOLCHAIN_FILE=$(OPENJ9OMR_TOPDIR)/cmake/toolchains/$(OPENJDK_TARGET_CPU)-$(OPENJDK_TARGET_OS)-cross.cmake \
         -DCMAKE_FIND_ROOT_PATH=$(SYSROOT) \
-        -DOMR_EXE_LAUNCHER="qemu-$(OPENJDK_TARGET_CPU)-static;-L;$(SYSROOT)"
+        -DOMR_EXE_LAUNCHER="qemu-$(OPENJDK_TARGET_CPU)-static;-L;$(SYSROOT)" \
+        -DCMAKE_BUILD_TYPE=Debug \
+        -DCMAKE_EXPORT_COMPILE_COMMANDS=ON
     else
       ifneq (,$(OPENJ9_CC))
         CMAKE_ARGS += -DCMAKE_C_COMPILER="$(OPENJ9_CC)"