Isolate serial loop #1321

Job	Run time
build-frontend	18s
getvars / get-vars	6s
build-firmware (Wemos-D1-Mini-ESP32)	1m 25s
build-firmware (Wemos-Lolin-S2-Mini)	1m 42s
build-firmware (Wemos-Lolin-S3)	1m 50s
build-firmware (Wemos-Lolin-S3-Mini)	2m 2s
build-firmware (Waveshare_esp32_s3_zero)	1m 45s
build-firmware (Pishock-2023)	1m 24s
build-firmware (Pishock-Lite-2021)	1m 41s
build-firmware (Seeed-Xiao-ESP32C3)	1m 32s
build-firmware (Seeed-Xiao-ESP32S3)	2m 4s
build-firmware (DFRobot-Firebeetle2-ESP32E)	1m 45s
build-firmware (OpenShock-Core-V1)	1m 42s
build-firmware (OpenShock-Core-V2)	1m 47s
build-staticfs	39s
merge-partitions (Wemos-D1-Mini-ESP32)	19s
merge-partitions (Wemos-Lolin-S2-Mini)	22s
merge-partitions (Wemos-Lolin-S3)	28s
merge-partitions (Wemos-Lolin-S3-Mini)	20s
merge-partitions (Waveshare_esp32_s3_zero)	28s
merge-partitions (Pishock-2023)	20s
merge-partitions (Pishock-Lite-2021)	19s
merge-partitions (Seeed-Xiao-ESP32C3)	27s
merge-partitions (Seeed-Xiao-ESP32S3)	23s
merge-partitions (DFRobot-Firebeetle2-ESP32E)	29s
merge-partitions (OpenShock-Core-V1)	20s
merge-partitions (OpenShock-Core-V2)	26s
checkpoint-build	1s
cdn-upload-version-info	0s
cdn-upload-firmware	0s
cdn-bump-version	0s
checkpoint-cdn	0s
release	0s
	26m 24s

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