[openwrt/openwrt] build,json: fix compatibility with Python 3.5

[LEDE Commits]

ynezz pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/5b8b42c78b10957c6dea82eb7a3e56a227d16edd

commit 5b8b42c78b10957c6dea82eb7a3e56a227d16edd
Author: Paul Spooren <mail at aparcar.org>
AuthorDate: Sat Jul 11 18:44:55 2020 -1000

    build,json: fix compatibility with Python 3.5
    
    The f-string feature was introduced in Python 3.6. As Buildbots may run
    on Debian 9, which comes per default with Python 3.5, this would cause
    an issue. Instead of f-strings use the *legacy* `.format()` function.
    
    Signed-off-by: Paul Spooren <mail at aparcar.org>
---
 scripts/json_overview_image_info.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/json_overview_image_info.py b/scripts/json_overview_image_info.py
index c76a442840..ca6fbbc962 100755
--- a/scripts/json_overview_image_info.py
+++ b/scripts/json_overview_image_info.py
@@ -38,7 +38,7 @@ if output:
             "make",
             "--no-print-directory",
             "-C",
-            f"target/linux/{output['target'].split('/')[0]}",
+            "target/linux/{}".format(output['target'].split('/')[0]),
             "val.DEFAULT_PACKAGES",
             "val.ARCH_PACKAGES",
         ],