canfestival: comment on musl disable

Based on commit 4d00a4058b9e5 (can-festival: disable on musl) and a previous
fix attempt[1], add a comment explaining why build with musl is disabled.

[1] http://patchwork.ozlabs.org/patch/509731/

Cc: Arnout Vandecappelle <arnout@mind.be>
Cc: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/canfestival/Config.in

@@ -11,7 +11,7 @@ comment "canfestival needs a glibc or uClibc toolchain w/ threads and dynamic li
 config BR2_PACKAGE_CANFESTIVAL
 	bool "canfestival"
 	depends on BR2_PACKAGE_CANFESTIVAL_ARCH_SUPPORTS
-	depends on !BR2_TOOLCHAIN_USES_MUSL
+	depends on !BR2_TOOLCHAIN_USES_MUSL # sigval_t
 	depends on BR2_TOOLCHAIN_HAS_THREADS
 	depends on !BR2_STATIC_LIBS
 	help