I've been bitten by the option BR2_ENABLE_DEBUG which does not exactly do what the doc describes:


config BR2_ENABLE_DEBUG
        bool "build packages with debugging symbols"
        help
          Build packages with debugging symbols enabled. All libraries
          and binaries in the 'staging' directory will have debugging
          symbols, which allows remote debugging even if libraries and
          binaries are stripped on the target. Whether libraries and
          binaries are stripped on the target is controlled by the
          BR2_STRIP_* options below.


For a CMake package, this corresponds to `-DCMAKE_BUILD_TYPE=RelWithDebInfo`, however currently buildroot will pass  `-DCMAKE_BUILD_TYPE=Debug` which has the effect of generating a *non-optimized* build (i.e. -O0).

I suggest the following patch:

diff --git a/package/pkg-cmake.mk b/package/pkg-cmake.mk
index db78d897d826..0a7bee685096 100644
--- a/package/pkg-cmake.mk
+++ b/package/pkg-cmake.mk
@@ -257,7 +257,7 @@ $(HOST_DIR)/share/buildroot/toolchainfile.cmake:
                -e 's#@@TARGET_FC@@#$(subst $(HOST_DIR)/,,$(call qstrip,$(TARGET_FC)))#' \
                -e 's#@@CMAKE_SYSTEM_PROCESSOR@@#$(call qstrip,$(CMAKE_SYSTEM_PROCESSOR))#' \
                -e 's#@@TOOLCHAIN_HAS_FORTRAN@@#$(if $(BR2_TOOLCHAIN_HAS_FORTRAN),1,0)#' \
-               -e 's#@@CMAKE_BUILD_TYPE@@#$(if $(BR2_ENABLE_DEBUG),Debug,Release)#' \
+               -e 's#@@CMAKE_BUILD_TYPE@@#$(if $(BR2_ENABLE_DEBUG),RelWithDebInfo,Release)#' \
                $(TOPDIR)/support/misc/toolchainfile.cmake.in \
                > $@