doc: fix riscv64 info in platform list

Signed-off-by: Han Gao <[email protected]>

Author: RevySR

BUILDING.md

@@ -115,7 +115,7 @@ platforms. This is true regardless of entries in the table below.
 | GNU/Linux        | ppc64le >=power9 | kernel >= 4.18[^1], glibc >= 2.28 | Tier 2       | e.g. Ubuntu 20.04, RHEL 8            |
 | GNU/Linux        | s390x >=z14      | kernel >= 4.18[^1], glibc >= 2.28 | Tier 2       | e.g. RHEL 8                          |
 | GNU/Linux        | loong64          | kernel >= 5.19, glibc >= 2.36     | Experimental |                                      |
-| GNU/Linux        | riscv64          | kernel >= 5.19, glibc >= 2.36     | Experimental |                                      |
+| GNU/Linux        | riscv64          | kernel >= 4.15, glibc >= 2.27     | Experimental |                                      |
 | Windows          | x64              | >= Windows 10/Server 2016         | Tier 1       | [^2],[^3]                            |
 | Windows          | arm64            | >= Windows 10                     | Tier 2       |                                      |
 | macOS            | x64              | >= 13.5                           | Tier 1       | For notes about compilation see [^4] |