emacs-28 894dfe7: Fix native-compilation build from tarball on Cygwin

[Ken Brown]

branch: emacs-28
commit 894dfe70da2dbeb218e8a0a58ee5e860f0fe9e4e
Author: Ken Brown <kbrown@cornell.edu>
Commit: Ken Brown <kbrown@cornell.edu>

    Fix native-compilation build from tarball on Cygwin
    
    * src/Makefile.in (../native-lisp) [CYGWIN]: Rebase the *.eln
    files after they are all created, to avoid fork problems later in
    the build.  (Bug#50666)
---
 src/Makefile.in | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/Makefile.in b/src/Makefile.in
index 759572f..b8d0e7b 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -806,6 +806,9 @@ elnlisp := $(addprefix ${lispsource}/,${elnlisp}) 
$(lisp:.elc=.eln)
 ../native-lisp: | $(pdmp)
        if test ! -d $@; then \
          mkdir $@ && $(MAKE) $(AM_V_NO_PD) $(elnlisp); \
+         if test $(SYSTEM_TYPE) = cygwin; then \
+           find $@ -name '*.eln' | rebase -v -O -T -; \
+         fi; \
          LC_ALL=C $(RUN_TEMACS) -batch $(BUILD_DETAILS) -l loadup 
--temacs=pdump \
                --bin-dest $(BIN_DESTDIR) --eln-dest $(ELN_DESTDIR) \
          && cp -f emacs$(EXEEXT) bootstrap-emacs$(EXEEXT) \