toolchain/musl: fix loongarch64 ldso file name

GCC has changed musl dynamic linker name from
ld-musl-loongarch-lp64d.so.1 to ld-musl-loongarch64.so.1 recently [1].

This means there are two dynamic linker names will be used across different
ersions of GCC. But musl 1.2.5 only supports the new name while the GCC
we're currently using uses the old name.

To maintain compatibility with all versions of GCC, the musl is then patched
to generate two symbolic links to libc.so with both old and new names.

[1] https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=8bccee51f0deac64b79cd9ad75df599422f4c8ff

Signed-off-by: Weijie Gao <hackpascal@gmail.com>

toolchain/musl/patches/400-fix-loongarch64-ldso-file-name.patch

@@ -0,0 +1,10 @@
+--- a/Makefile
++++ b/Makefile
+@@ -218,6 +218,7 @@ $(DESTDIR)$(includedir)/%: $(srcdir)/inc
+ 
+ $(DESTDIR)$(LDSO_PATHNAME): $(DESTDIR)$(libdir)/libc.so
+ 	$(INSTALL) -D -l libc.so $@ || true
++	$(if $(filter loongarch64,$(ARCH)$(SUBARCH)),$(INSTALL) -D -l libc.so $(subst $(ARCH)$(SUBARCH).so.1,loongarch-lp64d.so.1,$@) || true)
+ 
+ install-libs: $(ALL_LIBS:lib/%=$(DESTDIR)$(libdir)/%) $(if $(SHARED_LIBS),$(DESTDIR)$(LDSO_PATHNAME),)
+