vte: Use libstdc++ when using clang

It does not build with libc++ anymore.

Signed-off-by: Khem Raj <[email protected]>

conf/nonclangable.conf

@@ -354,6 +354,8 @@ CFLAGS:pn-pidgin-sipe:append:toolchain-clang = " -Wno-error=cast-function-type-s
 # v8 engine in nodejs moved beyong this commit
 # https://github.com/v8/v8/commit/d15d49b09dc7aef9edcc4cf6a0cb2b77a0db203f
 CXXFLAGS:pn-nodejs:append:toolchain-clang = " -Wno-error=enum-constexpr-conversion"
+# ../vte-0.78.0/src/color-test.cc:167:21: error: constexpr function never produces a constant expression [-Winvalid-constexpr]
+CXXFLAGS:pn-vte:append:toolchain-clang = " -Wno-error=invalid-constexpr"
 
 #| /usr/src/debug/ruby/2.5.1-r0/build/../ruby-2.5.1/process.c:7073: undefined reference to `__mulodi4'
 #| clang-7: error: linker command failed with exit code 1 (use -v to see invocation)
@@ -419,6 +421,10 @@ LIBCPLUSPLUS:pn-poco:toolchain-clang = "-stdlib=libstdc++"
 LIBCPLUSPLUS:pn-netdata:toolchain-clang = "-stdlib=libstdc++"
 LIBCPLUSPLUS:pn-cpp-netlib:toolchain-clang = "-stdlib=libstdc++"
 LIBCPLUSPLUS:pn-cpprest:toolchain-clang = "-stdlib=libstdc++"
+# ../vte-0.78.0/src/termprops.hh:392:31: error: no matching function for call to 'from_chars'
+#  392 |         if (auto [ptr, err] = std::from_chars(std::begin(str),
+#      |                               ^~~~~~~~~~~~~~~
+LIBCPLUSPLUS:pn-vte:toolchain-clang = "-stdlib=libstdc++"
 
 # Uses gcc for native tools, e.g. nsinstall and passes clang options which fails so
 # let same compiler ( gcc or clang) be native/cross compiler