Revert "fix: build installation dependencies before building consumers"

This reverts commit fb32ee6.

We cannot build all of the installation dependencies before building
some packages because there are apparent circular dependencies in some
cases.

Author: dhellmann

src/fromager/commands/build.py

@@ -638,17 +638,13 @@ def update_progressbar_cb(future: concurrent.futures.Future) -> None:
                 with req_ctxvar_context(
                     Requirement(node.canonicalized_name), node.version
                 ):
-                    # Get all dependencies. If package A needs package B to be
-                    # installed, package B should not have a build dependency on
-                    # package A. So, building the installation dependencies of a
-                    # package before we build that package should be possible,
-                    # and doing so ensures that when we mark a package as ready
-                    # to be used for building other packages, all of the
-                    # installation dependencies are also ready.
+                    # Get all build dependencies (build-system, build-backend, build-sdist)
                     build_deps: DependencyNodeList = [
-                        edge.destination_node for edge in node.children
+                        edge.destination_node
+                        for edge in node.children
+                        if edge.req_type.is_build_requirement
                     ]
-                    # A node can be built when all of its dependencies are built
+                    # A node can be built when all of its build dependencies are built
                     unbuilt_deps: set[str] = set(
                         dep.key for dep in build_deps if dep.key not in built_node_keys
                     )