modules/json-c: set cmake build type as minsizerel

[danielp96]

By default json-c builds as debug instead of release.

Adding CMAKE_BUILD_TYPE=minsizerel ensures it does not add debug info and optimizes for file size.

Fixes #1328

[tlaurion]

@danielp96 : awesome find!!!!! Thanks a lot for that!
Will check for build and redo build locally and compare lib and then merge!

[tlaurion]

Clean rebuild of 46aa253 happening at https://app.circleci.com/pipelines/github/tlaurion/heads/1595/workflows/873227a3-d591-4f43-9b84-2ca07cc1cc89 for comparison.

• PR's x230-hotp-maximized hashes https://app.circleci.com/pipelines/github/danielp96/heads/16/workflows/5e93e4fc-6d88-4309-bd0a-1b4974251527/jobs/565/parallel-runs/0/steps/0-104
  198c74e0fece1f69c96a02bb81ff19c0159bd997c201b30cd67018b6094d4e33 ./lib/libjson-c.so.5

• Local build hashes
  198c74e0fece1f69c96a02bb81ff19c0159bd997c201b30cd67018b6094d4e33 ./lib/libjson-c.so.5

• rebuild hashes.txt
  198c74e0fece1f69c96a02bb81ff19c0159bd997c201b30cd67018b6094d4e33 ./lib/libjson-c.so.5

[tlaurion]

Extending from linuxboot/heads-wiki#70 (comment) on local build vs this PR build:

user@heads-tests:/tmp$ HASHES1=~/heads/build/x86/x230-hotp-maximized/hashes.txt
user@heads-tests:/tmp$ HASHES2=/tmp/hashes.txt
user@heads-tests:/tmp$ egrep '^[0-9a-f]{64}' $HASHES1 | while read line; do HASH_REF=$(echo $line|awk -F " " {'print $1'}); FILE_REF=$(echo $line|awk -F "/" {'print $NF'}); if ! grep -q "$HASH_REF" $HASHES2; then echo "$FILE_REF doesn't match";fi; done
tools.cpio doesn't match
libmbedcrypto.so.0 doesn't match
libgcrypt.so.20 doesn't match
fbwhiptail doesn't match
kexec doesn't match
busybox doesn't match
bash doesn't match
initrd.cpio.xz doesn't match
heads-x230-hotp-maximized-v0.2.0-1508-g46aa253-bottom.rom doesn't match
heads-x230-hotp-maximized-v0.2.0-1508-g46aa253.rom doesn't match

[tlaurion]

@danielp96 thanks for that fix.