cmd/link: support PIE mode with internal link on linux arm64

cmd/link: support PIE mode with internal link on linux arm64

This CL improves internal link to provide basic support for cgo and PIE:
1, add support for GOT, PLT and GOTPLT.
2, add support for following ELF relocation types which have been used by std
   packages:
     R_AARCH64_ADR_GOT_PAGE
     R_AARCH64_LD64_GOT_LO12_NC
     R_AARCH64_ADR_PREL_PG_HI21
     R_AARCH64_ADD_ABS_LO12_NC
     R_AARCH64_LDST8_ABS_LO12_NC
     R_AARCH64_LDST32_ABS_LO12_NC
     R_AARCH64_LDST64_ABS_LO12_NC
     R_AARCH64_JUMP26
     R_AARCH64_ABS64
     R_AARCH64_PREL32
     R_AARCH64_PREL64

With this change, Go toolchain can be built in internal linking mode, and
pure Go programs can be built with PIE mode in internal linking mode on arm64.

Updates #10373
The prototype of this CL is contributed by Wei Xiao <wei.xiao@arm.com>

Change-Id: I2253923c69e855fd1524d54def309a961dce6247
Reviewed-on: https://go-review.googlesource.com/c/go/+/163579
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>