doc/build_wamr.md: Fix links to RISC-V named ABIs (#2852)

Fixes links to RISC-V application binary interface names.

Signed-off-by: Daniel Mangum <georgedanielmangum@gmail.com>

doc/build_wamr.md

@@ -27,8 +27,8 @@ The script `runtime_lib.cmake` defines a number of variables for configuring the
 - **WAMR_BUILD_TARGET**: set the target CPU architecture. Current supported targets are:  X86_64, X86_32, AARCH64, ARM, THUMB, XTENSA, ARC, RISCV32, RISCV64 and MIPS.
   - For ARM and THUMB, the format is \<arch>\[\<sub-arch>]\[_VFP], where \<sub-arch> is the ARM sub-architecture and the "_VFP" suffix means using VFP coprocessor registers s0-s15 (d0-d7) for passing arguments or returning results in standard procedure-call. Both \<sub-arch> and "_VFP" are optional, e.g. ARMV7, ARMV7_VFP, THUMBV7, THUMBV7_VFP and so on.
   - For AARCH64, the format is\<arch>[\<sub-arch>], VFP is enabled by default. \<sub-arch> is optional, e.g. AARCH64, AARCH64V8, AARCH64V8.1 and so on.
-  - For RISCV64, the format is \<arch\>[_abi], where "_abi" is optional, currently the supported formats are RISCV64, RISCV64_LP64D and RISCV64_LP64: RISCV64 and RISCV64_LP64D are identical, using [LP64D](https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-elf.md#-named-abis) as abi (LP64 with hardware floating-point calling convention for FLEN=64). And RISCV64_LP64 uses [LP64](https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-elf.md#-named-abis) as abi (Integer calling-convention only, and hardware floating-point calling convention is not used).
-  - For RISCV32, the format is \<arch\>[_abi], where "_abi" is optional, currently the supported formats are RISCV32, RISCV32_ILP32D and RISCV32_ILP32: RISCV32 and RISCV32_ILP32D are identical, using [ILP32D](https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-elf.md#-named-abis) as abi (ILP32 with hardware floating-point calling convention for FLEN=64). And RISCV32_ILP32 uses [ILP32](https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-elf.md#-named-abis) as abi (Integer calling-convention only, and hardware floating-point calling convention is not used).
+  - For RISCV64, the format is \<arch\>[_abi], where "_abi" is optional, currently the supported formats are RISCV64, RISCV64_LP64D and RISCV64_LP64: RISCV64 and RISCV64_LP64D are identical, using [LP64D](https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/master/riscv-cc.adoc#named-abis) as abi (LP64 with hardware floating-point calling convention for FLEN=64). And RISCV64_LP64 uses [LP64](https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/master/riscv-cc.adoc#named-abis) as abi (Integer calling-convention only, and hardware floating-point calling convention is not used).
+  - For RISCV32, the format is \<arch\>[_abi], where "_abi" is optional, currently the supported formats are RISCV32, RISCV32_ILP32D and RISCV32_ILP32: RISCV32 and RISCV32_ILP32D are identical, using [ILP32D](https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/master/riscv-cc.adoc#named-abis) as abi (ILP32 with hardware floating-point calling convention for FLEN=64). And RISCV32_ILP32 uses [ILP32](https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/master/riscv-cc.adoc#named-abis) as abi (Integer calling-convention only, and hardware floating-point calling convention is not used).
 
 ```bash
 cmake -DWAMR_BUILD_PLATFORM=linux -DWAMR_BUILD_TARGET=ARM