ci: test_build_system_cmake: ensure sdkconfig timestamp changes

idf.py bootloader runs very quickly on some build servers, so when
sdkconfig is modified, the next idf.py invocation doesn't pick up the
timestamp difference. Add some delays to make sure the change is
noticed.

tools/ci/test_build_system_cmake.sh

@@ -650,14 +650,17 @@ endmenu\n" >> ${IDF_PATH}/Kconfig
     idf.py bootloader || failure "Failed to build bootloader"
     bin_header_match build/bootloader/bootloader.bin "0210"
     # Change to 4MB
+    sleep 1 # delay here to make sure sdkconfig modification time is different
     echo "CONFIG_ESPTOOLPY_FLASHSIZE_4MB=y" > sdkconfig
     idf.py bootloader || failure "Failed to build bootloader"
     bin_header_match build/bootloader/bootloader.bin "0220"
     # Change to QIO, bootloader should still be DIO (will change to QIO in 2nd stage bootloader)
+    sleep 1 # delay here to make sure sdkconfig modification time is different
     echo "CONFIG_FLASHMODE_QIO=y" > sdkconfig
     idf.py bootloader || failure "Failed to build bootloader"
     bin_header_match build/bootloader/bootloader.bin "0210"
     # Change to 80 MHz
+    sleep 1 # delay here to make sure sdkconfig modification time is different
     echo "CONFIG_ESPTOOLPY_FLASHFREQ_80M=y" > sdkconfig
     idf.py bootloader || failure "Failed to build bootloader"
     bin_header_match build/bootloader/bootloader.bin "021f"