system-image-upgrader: only flash partition images if different

[JamiKettunen]

Do this by comparing checksums of the file vs partition bytes, also silence simgtest stderr spam on every non-sparse image file.

Log example including rtss timestamps to illustrate how long each step is taking on Volla Phone X23 with 20.04 OTA-2 flash to latest 20.04 devel:

$ rtss adb shell tail -f /cache/ubuntu_updater.log
  39.1ms   39.1ms | System Image Upgrader for Ubuntu Touch
  39.1ms          | Preparing command file
  39.1ms          | Starting image upgrader
  39.1ms          | Loading keyring: archive-master.tar.xz
  39.1ms          | Processing command file
  39.1ms          | Formatting: system
 174.9ms  135.8ms | system partition: /dev/block/dm-0
 211.6ms   36.7ms | umount: /mnt/system: Invalid argument
 223.1ms   11.6ms | mke2fs 1.45.4 (23-Sep-2019)
 241.3ms   18.2ms | Discarding device blocks: done                            
   1.09s    0.8ms | Creating filesystem with 2096128 4k blocks and 524288 inodes
   1.09s          | Filesystem UUID: ea2f26e9-e6a6-4589-bffb-0a3a71f80c50
   1.09s          | Superblock backups stored on blocks: 
   1.09s          |     32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632
   1.09s    0.3ms | 
   1.09s          | Allocating group tables: done                            
   1.10s    0.5ms | Writing inode tables: done                            
   1.10s    0.7ms | Creating journal (16384 blocks): done
   1.35s  250.1ms | Writing superblocks and filesystem accounting information: done 
   1.35s    5.3ms | 
   1.35s    3.1ms | Loading keyring: image-master.tar.xz
   1.74s  386.6ms | Loading keyring: image-signing.tar.xz
   2.23s  493.0ms | umount: /dev/block/dm-0: Invalid argument
   2.27s   39.4ms | umount: /cache/system: Invalid argument
   2.31s   37.9ms | umount: /mnt/system: Invalid argument
   2.32s   12.1ms | e2fsck 1.45.4 (23-Sep-2019)
   2.33s    6.4ms | Pass 1: Checking inodes, blocks, and sizes
   2.33s    4.5ms | Pass 2: Checking directory structure
   2.33s    0.6ms | Pass 3: Checking directory connectivity
   2.33s          | Pass 4: Checking reference counts
   2.35s   14.3ms | Pass 5: Checking group summary information
   2.36s    7.5ms | /dev/block/dm-0: 11/524288 files (0.0% non-contiguous), 49303/2096128 blocks
   2.40s   44.1ms | Unknown command: 
   2.40s    0.4ms | Keyring doesn't exist: device-signing
   7.76s    5.36s | Applying update: rootfs-8c8e0801737dbb104b95b2cdecdce88ed3934b78eb4a6e3903dd1a7f709b15fd.tar.xz
 1m0.92s   53.16s | Keyring doesn't exist: device-signing
 1m5.19s    4.27s | Applying update: firmware-068a5cdbd0dcff2904fd4b771b457404fa8848063062c71a83c9178cc8dcac6e.tar.xz
1m39.90s   34.70s | Checking if vendor at /dev/block/dm-1 needs updating...
1m47.17s    7.27s |   Flashing (cksum 360294409 != 1669154095)...
1m51.59s    4.42s | Checking if lk at /dev/block/by-name/lk_a needs updating...
1m51.74s  155.8ms |   Flashing (cksum 613770067 != 561110813)...
1m51.89s  146.2ms | Checking if tee at /dev/block/by-name/tee_a needs updating...
1m52.04s  148.2ms |   Flashing (cksum 1273672853 != 141589887)...
1m52.19s  152.2ms | Checking if scp at /dev/block/by-name/scp_a needs updating...
1m52.32s  129.4ms |   Flashing (cksum 1386461234 != 3847453068)...
1m52.47s  146.6ms | Checking if sspm at /dev/block/by-name/sspm_a needs updating...
1m52.59s  127.7ms |   Flashing (cksum 2066248718 != 1477994443)...
1m52.73s  134.9ms | Checking if dpm at /dev/block/by-name/dpm_a needs updating...
1m52.86s  127.0ms |   Flashing (cksum 1766797289 != 2369907974)...
1m53.00s  140.2ms | Checking if mcupm at /dev/block/by-name/mcupm_a needs updating...
1m53.12s  120.6ms |   Flashing (cksum 2896372325 != 2834491457)...
1m53.25s  135.8ms | Checking if md1img at /dev/block/by-name/md1img_a needs updating...
1m53.78s  524.0ms |   Flashing (cksum 3275156379 != 1595278505)...
1m54.18s  403.9ms | Checking if gz at /dev/block/by-name/gz_a needs updating...
1m54.31s  130.8ms |   Flashing (cksum 1431430420 != 1292548420)...
1m54.46s  143.9ms | Checking if spmfw at /dev/block/by-name/spmfw_a needs updating...
1m54.58s  121.7ms |   Flashing (cksum 2191500498 != 1392676407)...
1m54.71s  134.9ms | Checking if pi_img at /dev/block/by-name/pi_img_a needs updating...
1m54.83s  121.7ms |   Already up-to-date
1m54.99s  156.1ms | Keyring doesn't exist: device-signing
1m56.73s    1.74s | Applying update: device-83980d2d35082ad4f1f911079c4db009a38271327bffe0bd57388f2a31321caf.tar.xz
2m12.20s   15.48s | Keyring doesn't exist: device-signing
2m12.80s  600.1ms | Applying update: boot-3fe41f279fd6269ceff34f629adbb5cfcfeb46fa02271a4d05118c35be3fc2ec.tar.xz
2m16.43s    3.63s | Checking if boot at /dev/block/by-name/boot_a needs updating...
2m17.05s  612.7ms |   Flashing (cksum 3787133804 != 3814758713)...
2m18.57s    1.53s | Checking if vendor_boot at /dev/block/by-name/vendor_boot_a needs updating...
2m18.75s  177.9ms |   Flashing (cksum 4216945927 != 1030756222)...
2m18.95s  201.3ms | Checking if dtbo at /dev/block/by-name/dtbo_a needs updating...
2m19.07s  118.6ms |   Flashing (cksum 2893424597 != 1756549834)...
2m19.25s  177.5ms | Keyring doesn't exist: device-signing
2m19.26s   10.1ms | Applying update: keyring-400895c98ce498ca2d89a7ff0266361b427057d52e4be69b10118fbcbf2eef34.tar.xz
2m19.50s  239.4ms | Keyring doesn't exist: device-signing
2m19.51s   14.0ms | Applying update: version-385.tar.xz
2m20.28s  771.2ms | Done upgrading...
2m20.41s  128.7ms | tune2fs 1.45.4 (23-Sep-2019)
2m20.41s          | Setting reserved blocks percentage to 5% (645119 blocks)
2m21.48s    exit status: 0