configure: Improve detection of grpc_cpp_plugin.

When the `--with-libgrpc++=<path>` command line argument is given, add
`<path>/bin` to the search path for grpc_cpp_plugin.

diff --git a/configure.ac b/configure.ac
index e869a6a..6f947be 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -2635,6 +2635,7 @@ AC_ARG_WITH([libgrpc++],
     if test "x$withval" != "xno" && test "x$withval" != "xyes"; then
       with_libgrpcpp_cppflags="-I$withval/include"
       with_libgrpcpp_ldflags="-L$withval/lib"
+      with_libgrpcpp_bin="$withval/bin"
       with_libgrpcpp="yes"
     fi
     if test "x$withval" = "xno"; then
@@ -2714,7 +2715,11 @@ AC_SUBST([BUILD_WITH_LIBGRPCPP_LIBS])
 # }}}
 
 AC_ARG_VAR([GRPC_CPP_PLUGIN], [path to the grpc_cpp_plugin binary])
-AC_PATH_PROG([GRPC_CPP_PLUGIN], [grpc_cpp_plugin])
+if test "x$with_libgrpcpp_bin" = "x"; then
+  AC_PATH_PROG([GRPC_CPP_PLUGIN], [grpc_cpp_plugin])
+else
+  AC_PATH_PROG([GRPC_CPP_PLUGIN], [grpc_cpp_plugin], [], "$with_libgrpcpp_bin:$PATH")
+fi
 AM_CONDITIONAL([HAVE_GRPC_CPP], [test "x$GRPC_CPP_PLUGIN" != "x"])
 
 # --with-libiptc {{{