merge revision(s) 665b4c5b,642875e4,54b9b80b,361bce8d: [Backport #19967]

	[Bug #19967] Reset `LIBPATHENV` env after started

	Not to affect other tools invoked as child processes.
	---
	 common.mk            | 3 ++-
	 template/Makefile.in | 3 +++
	 template/fake.rb.in  | 3 +++
	 tool/fake.rb         | 8 ++++++++
	 4 files changed, 16 insertions(+), 1 deletion(-)

	[Bug #19967] Revert "configure.ac: LIBPATHENV on macOS"

	This reverts commit 1961c786.  These
	environment variables should no longer propagate to child processes.
	---
	 configure.ac | 2 +-
	 1 file changed, 1 insertion(+), 1 deletion(-)

	[Bug #19967] Delete real path

	---
	 tool/fake.rb | 3 ++-
	 1 file changed, 2 insertions(+), 1 deletion(-)

	[Bug #19967] Ignore library before build

	---
	 tool/fake.rb | 2 +-
	 1 file changed, 1 insertion(+), 1 deletion(-)