[PATCH] scripts/kernel-doc: Fix build time warnings

[André Almeida]

As stated at Documentation/kbuild/llvm.rst, to make usage of ccache one
must set KBUILD_BUILD_TIMESTAMP=''. Setting this together with W=1
will trigger the following warning for every compiled file:

  date: invalid date ‘+%s’

This comes from kernel-doc script, that produces the following command
when KBUILD_BUILD_TIMESTAMP is empty:

  date -d"" +%s

That triggers the warning above. Add a space between the flag `-d` and
the string argument to fix date command and remove the warning.

Signed-off-by: André Almeida <andrealmeid@xxxxxxxxxx>
---
 scripts/kernel-doc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/kernel-doc b/scripts/kernel-doc
index 2791f8195203..8728f9824c65 100755
--- a/scripts/kernel-doc
+++ b/scripts/kernel-doc
@@ -160,7 +160,7 @@ my @export_file_list;
 
 my @build_time;
 if (defined($ENV{'KBUILD_BUILD_TIMESTAMP'}) &&
-    (my $seconds = `date -d"${ENV{'KBUILD_BUILD_TIMESTAMP'}}" +%s`) ne '') {
+    (my $seconds = `date -d "${ENV{'KBUILD_BUILD_TIMESTAMP'}}" +%s`) ne '') {
     @build_time = gmtime($seconds);
 } else {
     @build_time = localtime;
-- 
2.47.0