package/uclibc: pass $(TARGET_DEBUGGING) flags

In order to have debugging symbols in uClibc, let's pass
$(TARGET_DEBUGGING) in UCLIBC_EXTRA_CFLAGS.

Signed-off-by: Ben Wolsieffer <Ben.Wolsieffer@hefring.com>
[Thomas: extracted from
https://patchwork.ozlabs.org/project/buildroot/patch/20220803200629.3172370-1-Ben.Wolsieffer@hefring.com/
and split into its own independent patch.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/uclibc/uclibc.mk

@@ -375,7 +375,7 @@ endif
 # Commands
 #
 
-UCLIBC_EXTRA_CFLAGS = $(TARGET_ABI)
+UCLIBC_EXTRA_CFLAGS = $(TARGET_ABI) $(TARGET_DEBUGGING)
 
 # uClibc-ng does not build with LTO, so explicitly disable it
 # when using a compiler that may have support for LTO