I'm searching for explanations of all the build-options. Especially, I'm searching for the stuff related to crypto:
I can't find any documentation.
TARGET_LEGACY_HW_DISK_ENCRYPTION is for Full Disk Encryption a.k.a. FDE.
TARGET_SWV8_DISK_ENCRYPTION is also a flag required for FDE I suppose .
TARGET_CRYPTFS_HW_PATH is the flag used to define the path of the files that will be used for hardware level FDE.
TARGET_KEYMASTER_WAIT_FOR_QSEE is the flag used for Qualcomm devices only. QSEE stands for Qualcomm Secure Execution Environment which is a Trusted Execution Environment (TEE). It is a secure area on Qualcomm chipsets where the Android OS and app developers can send data to be processed in a safe and secure environment. The QSEE cannot be accessed by no other app except for the application that has placed the data on the secure area. For More info about Encryption and KeyStore you can use for the following links for reference.
KeyStore: https://source.android.com/security/keystore
Encryption: https://source.android.com/security/encryption