compiler: link with lld on ARM (#733)

artiq/compiler/targets.py

@@ -68,6 +68,8 @@ class Target:
 
     :var triple: (string)
         LLVM target triple, e.g. ``"or1k"``
+    :var linker: (string)
+        Linker to run.
     :var data_layout: (string)
         LLVM target data layout, e.g. ``"E-m:e-p:32:32-i64:32-f64:32-v64:32-v128:32-a:0:32-n32"``
     :var features: (list of string)
@@ -84,6 +86,7 @@ class Target:
     triple = "unknown"
     data_layout = ""
     features = []
+    linker = "lld"
     print_function = "printf"
     little_endian = False
     now_pinning = True
@@ -176,7 +179,7 @@ class Target:
 
     def link(self, objects):
         """Link the relocatable objects into a shared library for this target."""
-        with RunTool([self.triple + "-ld", "-shared", "--eh-frame-hdr"] +
+        with RunTool([self.linker, "-shared", "--eh-frame-hdr"] +
                      ["{{obj{}}}".format(index) for index in range(len(objects))] +
                      ["-o", "{output}"],
                      output=None,
@@ -254,6 +257,7 @@ class OR1KTarget(Target):
     data_layout = "E-m:e-p:32:32-i8:8:8-i16:16:16-i64:32:32-" \
                   "f64:32:32-v64:32:32-v128:32:32-a0:0:32-n32"
     features = ["mul", "div", "ffl1", "cmov", "addc"]
+    linker = "or1k-linux-ld"
     print_function = "core_log"
     little_endian = False
     now_pinning = True
@@ -262,6 +266,7 @@ class CortexA9Target(Target):
     triple = "armv7-unknown-linux-gnueabihf"
     data_layout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
     features = ["dsp", "fp16", "neon", "vfp3"]
+    linker = "lld"
     print_function = "core_log"
     little_endian = True
     now_pinning = False