问题的解决方法是使用Bitbucket的REST API调用来获取最新的build状态，然后更新Pull Request的状态。下面是Python的代码示例：

import requests
import json

# Bitbucket REST API URL
url = "https://api.bitbucket.org/2.0/repositories/{username}/{repo_slug}/commit/{commit}/statuses/build"

# Bitbucket OAuth key and secret
consumer_key = "your-consumer-key"
consumer_secret = "your-consumer-secret"
access_token = "your-access-token"
access_token_secret = "your-access-token-secret"

# Build status payload
payload = {
    "state": "SUCCESSFUL",
    "key": "build",
    "url": "http://jenkins.example.com/build/1234",
    "name": "Jenkins Build"
}

# Bitbucket OAuth header
headers = {"Authorization": "OAuth oauth_consumer_key=\"{0}\", oauth_token=\"{1}\", oauth_signature_method=\"HMAC-SHA1\", oauth_signature=\"{2}\"".format(consumer_key, access_token, oauth_signature)}

# Get the commit hash of the latest build
r = requests.get("http://jenkins.example.com/build/api/json?tree=builds[timestamp,result,actions[lastBuiltRevision[SHA1]]]", auth=("jenkins-username", "jenkins-password"))
latest_build = json.loads(r.text)["builds"][0]["actions"][0]["lastBuiltRevision"]["SHA1"]

# Update the build status of the Pull Request
response = requests.post(url.format(username="your-username", repo_slug="your-repo-slug", commit=latest_build), auth=(consumer_key, consumer_secret, access_token, access_token_secret), headers=headers, json=payload)

print(response.text)

在此示例中，我们首先使用Jenkins API获得最后一个构建的操作。我们从此操作的JSON响应中提取Git提交哈希，然后调用Bitbucket REST API更新相应的PR的build状态。这会设置PR的build状态为成功。

如果需要处理失败的场景，可以根据需要修改payload。