hadrian: use stage0 linker to merge objects when done during the stage0

Fixes #18800.

2 files changed, 10 insertions, 0 deletions

diff --git a/hadrian/cfg/system.config.in b/hadrian/cfg/system.config.in
index 1297a2c1cc..8a3fb9341f 100644
--- a/hadrian/cfg/system.config.in
+++ b/hadrian/cfg/system.config.in
@@ -15,6 +15,7 @@ ld             = @LdCmd@
 make           = @MakeCmd@
 nm             = @NmCmd@
 merge-objects  = @MergeObjsCmd@
+system-merge-objects = @LD_STAGE0@
 objdump        = @ObjdumpCmd@
 ranlib         = @REAL_RANLIB_CMD@
 sphinx-build   = @SPHINXBUILD@
diff --git a/hadrian/src/Builder.hs b/hadrian/src/Builder.hs
index 743d169644..5d7ff33720 100644
--- a/hadrian/src/Builder.hs
+++ b/hadrian/src/Builder.hs
@@ -317,6 +317,15 @@ systemBuilderPath builder = case builder of
     Happy           -> fromKey "happy"
     HsCpp           -> fromKey "hs-cpp"
     Ld _            -> fromKey "ld"
+    -- MergeObjects Stage0 is a special case in case of
+    -- cross-compiling. We're building stage1, e.g. code which will be
+    -- executed on the host and hence we need to use host's merge
+    -- objects tool and not the target merge object tool.
+    -- Note, merge object tool is usually platform linker with some
+    -- parameters. E.g. building a cross-compiler on and for x86_64
+    -- which will target ppc64 means that MergeObjects Stage0 will use
+    -- x86_64 linker and MergeObject _ will use ppc64 linker.
+    MergeObjects Stage0 -> fromKey "system-merge-objects"
     MergeObjects _  -> fromKey "merge-objects"
     Make _          -> fromKey "make"
     Makeinfo        -> fromKey "makeinfo"