acpica: needs threads

Fixes:
  http://autobuild.buildroot.net/results/53e/53e38f278ad6d1a7d0a48bce74976f59475b1a99/
  http://autobuild.buildroot.net/results/a7c/a7cc6187451f944e6846d3f6b5cd3aac700796dd/

Signed-off-by: Erico Nunes <nunes.erico@gmail.com>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/acpica/Config.in

@@ -1,5 +1,6 @@
 config BR2_PACKAGE_ACPICA
 	bool "acpica"
+	depends on BR2_TOOLCHAIN_HAS_THREADS
 	help
 	  The ACPI Component Architecture (ACPICA) project provides an
 	  operating system (OS)-independent reference implementation
@@ -7,3 +8,6 @@ config BR2_PACKAGE_ACPICA
 	  Specification (ACPI).
 
 	  https://www.acpica.org
+
+comment "acpica needs a toolchain w/ threads"
+	depends on !BR2_TOOLCHAIN_HAS_THREADS