add configure option --enable-ld to use GNU gold or LLVM lld

https://lists.freedesktop.org/archives/libreoffice/2018-June/080437.html

Change-Id: I06214459fcebe5cc58fd7979f3cbe5ac3d97db7d
Reviewed-on: https://gerrit.libreoffice.org/56417
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>

config_host.mk.in

@@ -601,6 +601,7 @@ export UCRTSDKDIR=@UCRTSDKDIR@
 export UCRTVERSION=@UCRTVERSION@
 export UCRT_REDISTDIR=@UCRT_REDISTDIR@
 export UNOWINREG_DLL=@UNOWINREG_DLL@
+export USE_LD=@USE_LD@
 export USE_LIBRARY_BIN_TAR=@USE_LIBRARY_BIN_TAR@
 export USE_XINERAMA=@USE_XINERAMA@
 export UPDATE_CONFIG=@UPDATE_CONFIG@

configure.ac

@@ -1341,6 +1341,11 @@ AC_ARG_ENABLE(icecream,
          wrappers, you can override that using --with-gcc-home=/the/path switch.]),
 ,)
 
+AC_ARG_ENABLE(ld,
+    AS_HELP_STRING([--enable-ld=<linker>],
+        [Use the specified linker. Both 'gold' and 'lld' linkers generally use less memory and link faster.]),
+,)
+
 libo_FUZZ_ARG_ENABLE(cups,
     AS_HELP_STRING([--disable-cups],
         [Do not build cups support.])
@@ -3152,6 +3157,29 @@ else
 fi
 AC_SUBST(CROSS_COMPILING)
 
+USE_LD=
+if test -n "$enable_ld" -a "$enable_ld" != "no"; then
+    AC_MSG_CHECKING([for -fuse-ld=$enable_ld linker support])
+    if test "$GCC" = "yes"; then
+        ldflags_save=$LDFLAGS
+        LDFLAGS="$LDFLAGS -fuse-ld=$enable_ld"
+        AC_LINK_IFELSE([AC_LANG_PROGRAM([
+#include <stdio.h>
+            ],[
+printf ("hello world\n");
+            ])], USE_LD=$enable_ld, [])
+        if test -n "$USE_LD"; then
+            AC_MSG_RESULT( yes )
+            LDFLAGS="$ldflags_save -fuse-ld=$enable_ld"
+        else
+            AC_MSG_ERROR( no )
+        fi
+    else
+        AC_MSG_ERROR( not supported )
+    fi
+fi
+AC_SUBST(USE_LD)
+
 HAVE_LD_BSYMBOLIC_FUNCTIONS=
 if test "$GCC" = "yes"; then
     AC_MSG_CHECKING([for -Bsymbolic-functions linker support])

solenv/gbuild/platform/com_GCC_defs.mk

@@ -35,6 +35,10 @@ else
 gb_AR := $(shell $(CC) -print-prog-name=ar)
 endif
 
+ifneq ($(USE_LD),)
+gb_LinkTarget_LDFLAGS += -fuse-ld=$(USE_LD)
+endif
+
 ifeq ($(strip $(gb_COMPILEROPTFLAGS)),)
 gb_COMPILEROPTFLAGS := -O2
 endif