Strip leading zeroes from version (#21532)

When setting the Drake version automatically, strip leading zeroes in
order to maintain PEP 440 compliance. (Note that this logic is copied
from our CI drivers, which were already doing this.)

tools/install/libdrake/generate_version.cmake

@@ -24,7 +24,8 @@ if(DEFINED DRAKE_VERSION_OVERRIDE)
   set(DRAKE_VERSION "${DRAKE_VERSION_OVERRIDE}")
 else()
   string(TIMESTAMP BUILD_TIMESTAMP "%Y%m%d.%H%M%S")
-  set(DRAKE_VERSION "0.0.${BUILD_TIMESTAMP}+${BUILD_IDENTIFIER}")
+  string(REGEX REPLACE "[.]0+([0-9])" ".\\1"
+    DRAKE_VERSION "0.0.${BUILD_TIMESTAMP}+${BUILD_IDENTIFIER}")
 endif()
 
 configure_file(${INPUT_FILE} ${OUTPUT_FILE} @ONLY)