Merge branch 'clang_lto' into 'master'

Use the correct command line argument for the clang ipo

Closes #730

See merge request !1263

configure.ac

@@ -130,10 +130,8 @@ if test "$enable_ipo" = "yes"; then
                           ], [:] )
       AC_MSG_RESULT([added GCC interprocedural optimization support])
    elif test "$ax_cv_c_compiler_vendor" = "clang"; then
-      CFLAGS="$CFLAGS -flto -fuse-ld=gold"
-      LDFLAGS="$LDFLAGS -XCClinker -fuse-ld=gold"
-      : ${AR="llvm-ar"}
-      : ${LD="ld.gold"}
+      CFLAGS="$CFLAGS -flto=thin"
+      LDFLAGS="$LDFLAGS -flto=thin"
       : ${RANLIB="llvm-ranlib"}
       AC_MSG_RESULT([added LLVM interprocedural optimization support])
    else