build: Use ISO 8601 format for $(HOSTUTC)

In order to make the time format consistent for all host localizations
and systems, we use the ISO 8601 format for UTC.

Signed-off-by: Simon Kuenzer <simon@unikraft.io>
Reviewed-by: Cezar Craciunoiu <cezar.craciunoiu@unikraft.io>
Reviewed-by: Rares Miculescu <miculescur@gmail.com>
Approved-by: Razvan Deaconescu <razvand@unikraft.io>
GitHub-Closes: #1127

diff --git a/Makefile b/Makefile
index 8df14d93ea88684fc463f120fe855121b7630abe..eb908728d8a421bb4c7122d8e657a7afe434703a 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -440,7 +440,8 @@ HOSTOBJCOPY := $(shell which $(HOSTOBJCOPY) || type -p $(HOSTOBJCOPY) || echo ob
 HOSTRANLIB     := $(shell which $(HOSTRANLIB) || type -p $(HOSTRANLIB) || echo ranlib)
 HOSTCC_VERSION := $(shell $(HOSTCC_NOCCACHE) --version | \
                   $(SED) -n -r 's/^.* ([0-9]*)\.([0-9]*)\.([0-9]*)[ ]*.*/\1 \2/p')
-HOSTUTC                := $(shell date -u)
+# UTC time in ISO 8601 format:
+HOSTUTC                := $(shell date -Iseconds -u)
 HOSTNAME       := $(shell hostname -s)
 HOSTUSER       := $(shell whoami)