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: I72ef34689c60ce547cab2898e354b027e335f6a1
Exempt-From-Owner-Approval: build system cleanup
diff --git a/libbacktrace/Android.bp b/libbacktrace/Android.bp
index 69d7b6d..2f20684 100644
--- a/libbacktrace/Android.bp
+++ b/libbacktrace/Android.bp
@@ -83,7 +83,7 @@
         darwin: {
             enabled: true,
         },
-        linux: {
+        linux_glibc: {
             srcs: libbacktrace_sources,
 
             shared_libs: [
@@ -135,7 +135,7 @@
     srcs: ["backtrace_testlib.cpp"],
 
     target: {
-        linux: {
+        linux_glibc: {
             shared_libs: [
                 "libunwind",
                 "libunwindstack",
@@ -231,7 +231,7 @@
                 "libutils",
             ],
         },
-        linux: {
+        linux_glibc: {
             host_ldlibs: [
                 "-lncurses",
             ],