[PATCH v2] RISC-V: Implement TLS Descriptors.

This implements TLS Descriptors (TLSDESC) as specified in [1]. In TLSDESC instruction sequence, the first instruction relocates against the target TLS variable, while subsequent instructions relocates against the address of the first. Such usage of labels are not well-supported within GCC. Due to

[PATCH] RISC-V: Implement TLS Descriptors.

This implements TLS Descriptors (TLSDESC) as specified in [1]. In TLSDESC instruction sequence, the first instruction relocates against the target TLS variable, while subsequent instructions relocates against the address of the first. Such usage of labels are not well-supported within GCC. Due to