Fix libcompat not handling some external toolchain flags.

- Use libc++ with GCC.
- Use CROSS_BINUTILS_PREFIX with -B (r280980 addressed this mostly already)

Sponsored by:	EMC / Isilon Storage Division

Makefile.libcompat

@@ -52,7 +52,8 @@ LIBSOFTWMAKEFLAGS= -DCOMPAT_SOFTFP
 # Generic code for each type.
 # Set defaults based on type.
 libcompat= ${LIBCOMPAT:tl}
-_LIBCOMPAT_MAKEVARS= _OBJTREE TMP CPUFLAGS CFLAGS WMAKEENV WMAKEFLAGS WMAKE
+_LIBCOMPAT_MAKEVARS= _OBJTREE TMP CPUFLAGS CFLAGS CXXFLAGS WMAKEENV \
+ WMAKEFLAGS WMAKE
 .for _var in ${_LIBCOMPAT_MAKEVARS}
 .if !empty(LIB${LIBCOMPAT}${_var})
 LIBCOMPAT${_var}?= ${LIB${LIBCOMPAT}${_var}}
@@ -65,14 +66,21 @@ LIBCOMPATTMP?= ${OBJTREE}${.CURDIR}/lib${libcompat}
 
 LIBCOMPATCFLAGS+= ${LIBCOMPATCPUFLAGS} \
  -L${LIBCOMPATTMP}/usr/lib${libcompat} \
- --sysroot=${LIBCOMPATTMP}
+ --sysroot=${LIBCOMPATTMP} \
+ ${BFLAGS}
 
 # -B is needed to find /usr/lib32/crti.o for GCC and /usr/libsoft/crti.o for
 # Clang/GCC.
 LIBCOMPATCFLAGS+= -B${LIBCOMPATTMP}/usr/lib${libcompat}
 # GCC requires -isystem when using a cross-compiler.
 LIBCOMPATCFLAGS+= -isystem ${LIBCOMPATTMP}/usr/include
 
+.if defined(X_COMPILER_TYPE) && ${X_COMPILER_TYPE} == gcc
+# Force using libc++ for external GCC.
+LIBCOMPATCXXFLAGS+= -isystem ${LIBCOMPATTMP}/usr/include/c++/v1 -std=c++11 \
+ -nostdinc++ -L${LIBCOMPAT_OBJTREE}${.CURDIR}/lib/libc++
+.endif
+
 # Yes, the flags are redundant.
 LIBCOMPATWMAKEENV+= MAKEOBJDIRPREFIX=${LIBCOMPAT_OBJTREE} \
  INSTALL="sh ${.CURDIR}/tools/install.sh" \
@@ -81,7 +89,7 @@ LIBCOMPATWMAKEENV+= MAKEOBJDIRPREFIX=${LIBCOMPAT_OBJTREE} \
  SHLIBDIR=/usr/lib${libcompat} \
  DTRACE="${LIB$COMPATDTRACE:U${DTRACE}}"
 LIBCOMPATWMAKEFLAGS+= CC="${XCC} ${LIBCOMPATCFLAGS}" \
- CXX="${XCXX} ${LIBCOMPATCFLAGS}" \
+ CXX="${XCXX} ${LIBCOMPATCFLAGS} ${LIBCOMPATCXXFLAGS}" \
  DESTDIR=${LIBCOMPATTMP} \
  -DNO_CPU_CFLAGS \
  MK_CTF=no \