package/qt5base: fix uclibc/musl compile with libexecinfo enabled

- depend and link against libexecinfo if enabled to fix linking failure
  in case execinfo.h is detected for qlogging:

  qt5base-5.15.2/src/corelib/global/qlogging.cpp:110 - __has_include(<execinfo.h>)

- libexecinfo already depends on !BR2_TOOLCHAIN_USES_GLIBC

- rename plain QT5BASE_CONFIGURE_ARCH_CONFIG to QT5BASE_CONFIGURE_ARCH_CONFIG_LIBATOMIC

Fixes:

  - http://autobuild.buildroot.net/results/e7c685744b1f1bebb7fec9835bda534a72b7b7c2

  .../riscv64-buildroot-linux-musl/bin/ld: .../build/qt5base-5.15.2/src/corelib/global/qlogging.cpp:1398: undefined reference to `backtrace_symbols'

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/qt5/qt5base/qt5base.mk

@@ -235,6 +235,14 @@ QT5BASE_DEPENDENCIES   += $(if $(BR2_PACKAGE_QT5BASE_ICU),icu)
 
 QT5BASE_CONFIGURE_OPTS += $(if $(BR2_PACKAGE_QT5BASE_EXAMPLES),-make,-nomake) examples
 
+# see qt5base-5.15.2/src/corelib/global/qlogging.cpp:110 - __has_include(<execinfo.h>)
+ifeq ($(BR2_PACKAGE_LIBEXECINFO),y)
+QT5BASE_DEPENDENCIES += libexecinfo
+define QT5BASE_CONFIGURE_ARCH_CONFIG_LIBEXECINFO
+	printf '!host_build { \n LIBS += -lexecinfo\n }' >$(QT5BASE_ARCH_CONFIG_FILE)
+endef
+endif
+
 ifeq ($(BR2_PACKAGE_LIBINPUT),y)
 QT5BASE_CONFIGURE_OPTS += -libinput
 QT5BASE_DEPENDENCIES += libinput
@@ -283,7 +291,7 @@ endif
 QT5BASE_ARCH_CONFIG_FILE = $(@D)/mkspecs/devices/linux-buildroot-g++/arch.conf
 ifeq ($(BR2_TOOLCHAIN_HAS_LIBATOMIC),y)
 # Qt 5.8 needs atomics, which on various architectures are in -latomic
-define QT5BASE_CONFIGURE_ARCH_CONFIG
+define QT5BASE_CONFIGURE_ARCH_CONFIG_LIBATOMIC
 	printf '!host_build { \n LIBS += -latomic\n }' >$(QT5BASE_ARCH_CONFIG_FILE)
 endef
 endif
@@ -306,7 +314,8 @@ define QT5BASE_CONFIGURE_CMDS
 		$(@D)/mkspecs/devices/linux-buildroot-g++/qplatformdefs.h
 	$(QT5BASE_CONFIGURE_CONFIG_FILE)
 	touch $(QT5BASE_ARCH_CONFIG_FILE)
-	$(QT5BASE_CONFIGURE_ARCH_CONFIG)
+	$(QT5BASE_CONFIGURE_ARCH_CONFIG_LIBATOMIC)
+	$(QT5BASE_CONFIGURE_ARCH_CONFIG_LIBEXECINFO)
 	$(QT5BASE_CONFIGURE_HOSTCC)
 	(cd $(@D); \
 		$(TARGET_MAKE_ENV) \