package/kmsxx: fix fmt dependency (needs wchar)

Propagate the fmt dependency on wchar.

Fixes:

 - http://autobuild.buildroot.net/results/814b0f9c3df0076791ca73579b844ef4d56f13c3

  [ 66%] Building CXX object CMakeFiles/fmt.dir/src/os.cc.o
  In file included from .../build/fmt-7.1.3/include/fmt/os.h:26,
                   from .../build/fmt-7.1.3/src/os.cc:13:
  .../build/fmt-7.1.3/include/fmt/format.h:1139:8: error: 'wstring' in namespace 'std' does not name a type
     std::wstring str() const { return {&buffer_[0], size()}; }
          ^~~~~~~

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/kmsxx/Config.in

@@ -4,6 +4,7 @@ config BR2_PACKAGE_KMSXX
 	depends on BR2_TOOLCHAIN_HEADERS_AT_LEAST_4_11 # linux/dma-buf.h
 	depends on BR2_INSTALL_LIBSTDCPP
 	depends on BR2_TOOLCHAIN_HAS_THREADS # libdrm
+	depends on BR2_USE_WCHAR # fmt
 	select BR2_PACKAGE_FMT
 	select BR2_PACKAGE_LIBDRM
 	help
@@ -22,6 +23,7 @@ config BR2_PACKAGE_KMSXX_INSTALL_TESTS
 
 endif
 
-comment "kms++ needs a toolchain w/ threads, C++, gcc >= 4.8, headers >= 4.11"
+comment "kms++ needs a toolchain w/ threads, C++, gcc >= 4.8, headers >= 4.11, wchar"
 	depends on !BR2_TOOLCHAIN_HAS_THREADS || !BR2_INSTALL_LIBSTDCPP || \
-		!BR2_TOOLCHAIN_GCC_AT_LEAST_4_8 || !BR2_TOOLCHAIN_HEADERS_AT_LEAST_4_11
+		!BR2_TOOLCHAIN_GCC_AT_LEAST_4_8 || !BR2_TOOLCHAIN_HEADERS_AT_LEAST_4_11 \
+		|| !BR2_USE_WCHAR