[gcc r11-4640] libstdc++: use lt_host_flags for libstdc++.la

[Jonathan Wakely]

https://gcc.gnu.org/g:08fca4df1db9b1ec09c846a8b415bd652cc48050

commit r11-4640-g08fca4df1db9b1ec09c846a8b415bd652cc48050
Author: Jonathan Yong <10walls@gmail.com>
Date:   Tue Nov 3 07:47:12 2020 +0000

    libstdc++: use lt_host_flags for libstdc++.la
    
    For platforms like Mingw and Cygwin, cygwin refuses to generate the
    shared library without using -no-undefined.
    
    Attached patch makes sure the right flags are used, since libtool is
    already used to link libstdc++.
    
    libstdc++-v3/ChangeLog:
    
            * src/Makefile.am (libstdc___la_LINK): Add lt_host_flags.
            * src/Makefile.in: Regenerate.

Diff:
---
 libstdc++-v3/src/Makefile.am | 2 +-
 libstdc++-v3/src/Makefile.in | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/src/Makefile.am b/libstdc++-v3/src/Makefile.am
index 9a6807ae8c6..1eda70edb37 100644
--- a/libstdc++-v3/src/Makefile.am
+++ b/libstdc++-v3/src/Makefile.am
@@ -110,7 +110,7 @@ libstdc___la_DEPENDENCIES = \
 libstdc___la_LDFLAGS = \
 	-version-info $(libtool_VERSION) ${version_arg} -lm
 
-libstdc___la_LINK = $(CXXLINK) $(libstdc___la_LDFLAGS)
+libstdc___la_LINK = $(CXXLINK) $(libstdc___la_LDFLAGS) $(lt_host_flags)
 
 # Use special rules for compatibility-ldbl.cc compilation, as we need to
 # pass -mlong-double-64.
diff --git a/libstdc++-v3/src/Makefile.in b/libstdc++-v3/src/Makefile.in
index e51e6164055..7f559171355 100644
--- a/libstdc++-v3/src/Makefile.in
+++ b/libstdc++-v3/src/Makefile.in
@@ -519,7 +519,7 @@ libstdc___la_DEPENDENCIES = \
 libstdc___la_LDFLAGS = \
 	-version-info $(libtool_VERSION) ${version_arg} -lm
 
-libstdc___la_LINK = $(CXXLINK) $(libstdc___la_LDFLAGS)
+libstdc___la_LINK = $(CXXLINK) $(libstdc___la_LDFLAGS) $(lt_host_flags)
 
 # A note on compatibility and static libraries.
 #