Tweak linux_glibc properties for musl builds in bionic

For convenience, builds against musl libc currently use the
linux_glibc properties because they are almost always linux-specific
and not glibc-specific.  In preparation for removing this hack,
tweak the linux_glibc properties by either moving them to host_linux,
which will apply to linux_glibc, linux_musl and linux_bionic, or
by setting appropriate musl or linux_musl properties.  Properties
that must not be repeated while musl uses linux_musl and also still
uses the linux_glibc properties are moved to glibc properties, which
don't apply to musl.  Whether these stay as glibc properties or get
moved back to linux_glibc later once the musl hack is removed is TBD.

Bug: 223257095
Test: m checkbuild
Test: m USE_HOST_MUSL=true host-native
Change-Id: I809bf1ba783dff02f6491d87fbdc9fa7fc0975b0
diff --git a/benchmarks/spawn/Android.bp b/benchmarks/spawn/Android.bp
index 89d22e3..61e7bf6 100644
--- a/benchmarks/spawn/Android.bp
+++ b/benchmarks/spawn/Android.bp
@@ -43,6 +43,9 @@
         linux_glibc_x86: {
             enabled: false,
         },
+        linux_musl_x86: {
+            enabled: false,
+        },
     },
 }
 
@@ -103,6 +106,11 @@
                 "-Wl,--rpath,${ORIGIN}/../../lib64",
             ],
         },
+        linux_musl_x86_64: {
+            ldflags: [
+                "-Wl,--rpath,${ORIGIN}/../../lib64",
+            ],
+        },
     },
 }