qt5: disallow 5.8 version for ARMv4

Fixes:
http://autobuild.buildroot.net/results/197/197ab8a12bf1d780a986e5d447d1e0f5ee070405/

qt5.8 no longer supports ARMv4. From src/corelib/global/qprocessordetection.h:

  if Q_PROCESSOR_ARM >= 6
    define Q_PROCESSOR_ARM_V6
  endif
  if Q_PROCESSOR_ARM >= 5
    define Q_PROCESSOR_ARM_V5
  else
    error "ARM architecture too old"

[Peter: also hide comment as pointed out by Baruch]
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/qt5/Config.in

@@ -38,12 +38,14 @@ config BR2_PACKAGE_QT5_VERSION_LATEST
 	bool "Latest (5.8)"
 	depends on BR2_TOOLCHAIN_GCC_AT_LEAST_4_8 # C++11
 	depends on BR2_HOST_GCC_AT_LEAST_4_8 # C++11
+	depends on !BR2_ARM_CPU_ARMV4 # needs ARMv5+
 	help
 	  This option builds Qt 5.8, which is licensed under
 	  (L)GPLv3+.
 
 comment "Latest Qt version needs host/toolchain w/ gcc >= 4.8"
 	depends on !BR2_TOOLCHAIN_GCC_AT_LEAST_4_8 || !BR2_HOST_GCC_AT_LEAST_4_8
+	depends on !BR2_ARM_CPU_ARMV4
 
 config BR2_PACKAGE_QT5_VERSION_5_6
 	bool "LTS (5.6)"