Update build_version.cc.in

Author: chejinge

src/build_version.cc.in

@@ -7,4 +7,4 @@
 const char* pika_build_git_sha =
               "pika_git_sha:@PIKA_GIT_SHA@";
 const char* pika_build_git_date = "pika_build_git_date:@PIKA_GIT_DATE@";
-const char* pika_build_compile_date = "pika_build_date:@PIKA_BUILD_DATE@";
+const char* pika_build_compile_date = "@PIKA_BUILD_DATE@";