bswap: add RISC-V support.

[pengjunjie2100]

Description of PR

The intention of this PR is to support bswap native function on riscv . Without this part of the change, compiling the bswap related code on RISCV will result in an error.This part of the change is controlled by the compilation macro and will not affect running on other architecture.

How was this patch tested?

unit test

For code changes:

• Does the title or this PR starts with the corresponding JIRA issue id (e.g. 'HADOOP-17799. Your PR title ...')?
• Object storage: have the integration tests been executed and the endpoint declared according to the connector-specific documentation?
• If adding new dependencies to the code, are these dependencies licensed in a way that is compatible for inclusion under ASF 2.0?
• If applicable, have you updated the LICENSE, LICENSE-binary, NOTICE-binary files?

[pan3793]

How was this patch tested?

unit test

where is it?

[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	39m 44s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 1s		No case conflicting files found.
+0 🆗	codespell	0m 0s		codespell was not available.
+0 🆗	detsecrets	0m 0s		detect-secrets was not available.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
-1 ❌	test4tests	0m 0s		The patch doesn't appear to include any new or modified tests. Please justify why no new tests are needed for this patch. Also please list what manual steps were performed to verify this patch.
			_ trunk Compile Tests _
-1 ❌	mvninstall	37m 37s	/branch-mvninstall-root.txt	root in trunk failed.
+1 💚	compile	0m 58s		trunk passed
+1 💚	mvnsite	0m 35s		trunk passed
+1 💚	shadedclient	73m 37s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	0m 21s		the patch passed
-1 ❌	compile	0m 38s	/patch-compile-hadoop-mapreduce-project_hadoop-mapreduce-client_hadoop-mapreduce-client-nativetask.txt	hadoop-mapreduce-client-nativetask in the patch failed.
-1 ❌	cc	0m 38s	/patch-compile-hadoop-mapreduce-project_hadoop-mapreduce-client_hadoop-mapreduce-client-nativetask.txt	hadoop-mapreduce-client-nativetask in the patch failed.
-1 ❌	golang	0m 38s	/patch-compile-hadoop-mapreduce-project_hadoop-mapreduce-client_hadoop-mapreduce-client-nativetask.txt	hadoop-mapreduce-client-nativetask in the patch failed.
-1 ❌	javac	0m 39s	/patch-compile-hadoop-mapreduce-project_hadoop-mapreduce-client_hadoop-mapreduce-client-nativetask.txt	hadoop-mapreduce-client-nativetask in the patch failed.
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	mvnsite	0m 22s		the patch passed
+1 💚	shadedclient	34m 26s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
-1 ❌	unit	0m 43s	/patch-unit-hadoop-mapreduce-project_hadoop-mapreduce-client_hadoop-mapreduce-client-nativetask.txt	hadoop-mapreduce-client-nativetask in the patch failed.
+1 💚	asflicense	0m 41s		The patch does not generate ASF License warnings.
		152m 3s

Subsystem	Report/Notes
Docker	ClientAPI=1.51 ServerAPI=1.51 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-7787/1/artifact/out/Dockerfile
GITHUB PR	#7787
Optional Tests	dupname asflicense compile cc mvnsite javac unit codespell detsecrets golang
uname	Linux 0bf05e8881d4 5.15.0-143-generic #153-Ubuntu SMP Fri Jun 13 19:10:45 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / 31d147c
Default Java	Red Hat, Inc.-1.8.0_412-b08
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-7787/1/testReport/
Max. process+thread count	552 (vs. ulimit of 5500)
modules	C: hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-nativetask U: hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-nativetask
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-7787/1/console
versions	git=2.9.5 maven=3.6.3
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