Use non-throwing is_directory in filesystem::create_directory

[Jonathan Wakely]

The create_dir helper was calling the throwing form of
filesystem::is_directory instead of passing the error_code argument.
Since std::filesystem::create_directory(const path&, error_code&) is
noexcept, it would call std::terminate if an error occurred in
is_directory.

Passing the error_code also takes care of clearing it in the case where
is_directory returns true.

            src/filesystem/ops.cc (create_dir): Pass error_code to is_directory.
            src/filesystem/std-ops.cc (create_dir): Likewise.

Tested powerpc64le-linux, committed to trunk.
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commit c3ac5f5cbb2ce9d20c30da06d19bcdca20630e0b
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Mar 9 00:42:20 2018 +0000

    Use non-throwing is_directory in filesystem::create_directory
    
    The create_dir helper was calling the throwing form of
    filesystem::is_directory instead of passing the error_code argument.
    Since std::filesystem::create_directory(const path&, error_code&) is
    noexcept, it would call std::terminate if an error occurred in
    is_directory.
    
    Passing the error_code also takes care of clearing it in the case where
    is_directory returns true.
    
            src/filesystem/ops.cc (create_dir): Pass error_code to is_directory.
            src/filesystem/std-ops.cc (create_dir): Likewise.

diff --git a/libstdc++-v3/src/filesystem/ops.cc b/libstdc++-v3/src/filesystem/ops.cc
index 899defea6d2..328332a8a82 100644
--- a/libstdc++-v3/src/filesystem/ops.cc
+++ b/libstdc++-v3/src/filesystem/ops.cc
@@ -463,10 +463,8 @@ namespace
     if (::mkdir(p.c_str(), mode))
       {
 	const int err = errno;
-	if (err != EEXIST || !is_directory(p))
+	if (err != EEXIST || !is_directory(p, ec))
 	  ec.assign(err, std::generic_category());
-	else
-	  ec.clear();
       }
     else
       {
diff --git a/libstdc++-v3/src/filesystem/std-ops.cc b/libstdc++-v3/src/filesystem/std-ops.cc
index 65b06f5b67b..930b186e88c 100644
--- a/libstdc++-v3/src/filesystem/std-ops.cc
+++ b/libstdc++-v3/src/filesystem/std-ops.cc
@@ -668,10 +668,8 @@ namespace
     if (::mkdir(p.c_str(), mode))
       {
 	const int err = errno;
-	if (err != EEXIST || !is_directory(p))
+	if (err != EEXIST || !is_directory(p, ec))
 	  ec.assign(err, std::generic_category());
-	else
-	  ec.clear();
       }
     else
       {