boost: add option for the stacktrace library

stacktrace requires dynamic library support, which was causing the
following build errors:

http://autobuild.buildroot.net/results/692ffad93a7bd867ecc7ccbfc8c6280735d29435/
http://autobuild.buildroot.net/results/6058ece804889abaaab0a29258e1de2904162d26/
http://autobuild.buildroot.net/results/12df9b345a90a4e011b8bb4cb1d1ef1c2c7040c0/
http://autobuild.buildroot.net/results/7473c433e93b3e785e44d9868fec517437f59847/

Adding an option for it allows to have it disabled by default, and
make sure it only gets enabled when shared library support is
available.

Signed-off-by: Adam Duskett <aduskett@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/boost/Config.in

@@ -158,6 +158,15 @@ config BR2_PACKAGE_BOOST_SERIALIZATION
 config BR2_PACKAGE_BOOST_SIGNALS
 	bool "boost-signals"
 
+config BR2_PACKAGE_BOOST_STACKTRACE
+	bool "boost-stacktrace"
+	depends on !BR2_STATIC_LIBS
+	help
+	  Gather, store, copy and print backtraces.
+
+comment "boost-stacktrace needs a toolchain w/ dynamic library"
+	depends on BR2_STATIC_LIBS
+
 config BR2_PACKAGE_BOOST_SYSTEM
 	bool "boost-system"
 

package/boost/boost.mk

@@ -42,6 +42,7 @@ BOOST_WITHOUT_FLAGS += $(if $(BR2_PACKAGE_BOOST_RANDOM),,random)
 BOOST_WITHOUT_FLAGS += $(if $(BR2_PACKAGE_BOOST_REGEX),,regex)
 BOOST_WITHOUT_FLAGS += $(if $(BR2_PACKAGE_BOOST_SERIALIZATION),,serialization)
 BOOST_WITHOUT_FLAGS += $(if $(BR2_PACKAGE_BOOST_SIGNALS),,signals)
+BOOST_WITHOUT_FLAGS += $(if $(BR2_PACKAGE_BOOST_STACKTRACE),,stacktrace)
 BOOST_WITHOUT_FLAGS += $(if $(BR2_PACKAGE_BOOST_SYSTEM),,system)
 BOOST_WITHOUT_FLAGS += $(if $(BR2_PACKAGE_BOOST_TEST),,test)
 BOOST_WITHOUT_FLAGS += $(if $(BR2_PACKAGE_BOOST_THREAD),,thread)