boost: do not allow boost-log on PowerPC with uClibc

The build of boost-log with a uClibc toolchain on PowerPC fails with
some weird C++ issues. Since nobody ever looked into this problem,
let's "fix" the autobuilder issue by not allowing to select boost-log
in such a situation.

Fixes:

   http://autobuild.buildroot.net/results/13b43105caf4d3952de70030b51f8d96cf6604ee/
   (and many, many similar build failures)

[Peter: also add dependency to comment]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/boost/Config.in

@@ -99,9 +99,13 @@ comment "boost-locale needs a toolchain w/ wchar"
 config BR2_PACKAGE_BOOST_LOG
 	bool "boost-log"
 	depends on BR2_TOOLCHAIN_HAS_THREADS_NPTL
+	# for some reason, uClibc on PowerPC fails to build the boost
+	# log module
+	depends on !(BR2_powerpc && BR2_TOOLCHAIN_USES_UCLIBC)
 
 comment "boost-log needs a toolchain w/ NPTL"
 	depends on !BR2_TOOLCHAIN_HAS_THREADS_NPTL
+	depends on !(BR2_powerpc && BR2_TOOLCHAIN_USES_UCLIBC)
 
 config BR2_PACKAGE_BOOST_MATH
 	bool "boost-math"