Convert test binaries to C++ (#2235)

This ensures that they are compiled with a consistent compiler and set of flags
as the rest of s3fs.

test/Makefile.am

@@ -36,11 +36,20 @@ noinst_PROGRAMS = \
     truncate_read_file \
     cr_filename
 
-junk_data_SOURCES          = junk_data.c
+junk_data_SOURCES          = junk_data.cc
 write_multiblock_SOURCES   = write_multiblock.cc
-mknod_test_SOURCES         = mknod_test.c
+mknod_test_SOURCES         = mknod_test.cc
-truncate_read_file_SOURCES = truncate_read_file.c
+truncate_read_file_SOURCES = truncate_read_file.cc
-cr_filename_SOURCES        = cr_filename.c
+cr_filename_SOURCES        = cr_filename.cc
+
+clang-tidy:
+	clang-tidy \
+    $(junk_data_SOURCES) \
+    $(write_multiblock_SOURCES) \
+    $(mknod_test_SOURCES) \
+    $(truncate_read_file_SOURCES) \
+    $(cr_filename_SOURCES) \
+    -- $(DEPS_CFLAGS) $(CPPFLAGS)
 
 #
 # Local variables:

test/junk_data.cc

@@ -34,7 +34,7 @@ int main(int argc, const char *argv[])
     for (i = 0; i < count; i += sizeof(buf)) {
         long long j;
         for (j = 0; j < sizeof(buf) / sizeof(i); ++j) {
-            *((long long *)buf + j) = i / sizeof(i) + j;
+            *(reinterpret_cast<long long *>(buf) + j) = i / sizeof(i) + j;
         }
         fwrite(buf, 1, sizeof(buf) > count - i ? count - i : sizeof(buf), stdout);
     }