Rename target.linux[_x86[_64]] to target.linux_glibc[_x86[_64]]

In the future, target.linux will apply to all targets running a linux kernel
(android, linux_glibc, linux_bionic). So move all current users to the specific
linux_glibc.

There will be another cleanup pass later that will move some instances back to
target.linux if the properties should be shared with target.android and
target.linux_bionic, but target.linux needs to be removed first.

Test: out/soong/build.ninja identical before/after
Change-Id: I1afccdd2f5d29c9516fdc14d9fd222efb796900e
Exempt-From-Owner-Approval: build system cleanup
diff --git a/Android.bp b/Android.bp
index ec3e717..a337dfc 100644
--- a/Android.bp
+++ b/Android.bp
@@ -165,7 +165,7 @@
     ],
     enabled: false,
     target: {
-        linux_x86_64: {
+        linux_glibc_x86_64: {
             enabled: true,
         },
     },