Don't link against explicit instances of libm, librt, etc..

The current way adds unnecessary RPATH entries into the binaries that
aren't helpful. This patch just adds linkopts to the apprpriate
targets to let the linker decide what to do.

This should allow us to run binaries on Debian 8 that were compiled on
Debian 9 with a sandboxed compiler.

Change-Id: Icdec2ffbd12f83b72a4ab678b8fcbbb2adc12bc5
diff --git a/frc971/control_loops/BUILD b/frc971/control_loops/BUILD
index 5998afc..4951d86 100644
--- a/frc971/control_loops/BUILD
+++ b/frc971/control_loops/BUILD
@@ -72,7 +72,9 @@
         ":gaussian_noise",
         ":queues",
         "//aos/testing:random_seed",
-        "//debian:libm",
+    ],
+    linkopts = [
+        "-lm",
     ],
 )
 
@@ -84,8 +86,8 @@
     hdrs = [
         "gaussian_noise.h",
     ],
-    deps = [
-        "//debian:libm",
+    linkopts = [
+        "-lm",
     ],
 )
 
@@ -114,9 +116,11 @@
     ],
     deps = [
         "//aos/common/controls:polytope",
-        "//debian:libm",
         "//third_party/eigen",
     ],
+    linkopts = [
+        "-lm",
+    ],
 )
 
 # TODO(austin): Select isn't working right.  We should be able to remove