Remove (C|CPP|CONLY|LD)FLAGS checked by Soong

At the beginning of every build, Soong has exported its version of these
variables, and has been ensuring that when sorted, the result is the
same. So these variables all have the same flags of the Soong ones, but
may be in different orders. We don't believe any of the remaining order
differences matter. As we remove the Make definitions, the exported
Soong variables will take over.

This only removes lines that change one of these variables:

  [2ND_][CLANG_]HOST_CROSS_GLOBAL_CFLAGS
  [2ND_][CLANG_]HOST_CROSS_GLOBAL_CONLYFLAGS
  [2ND_][CLANG_]HOST_CROSS_GLOBAL_CPPFLAGS
  [2ND_][CLANG_]HOST_CROSS_GLOBAL_LDFLAGS
  [2ND_][CLANG_]HOST_GLOBAL_CFLAGS
  [2ND_][CLANG_]HOST_GLOBAL_CONLYFLAGS
  [2ND_][CLANG_]HOST_GLOBAL_CPPFLAGS
  [2ND_][CLANG_]HOST_GLOBAL_LDFLAGS
  [2ND_][CLANG_]TARGET_GLOBAL_CFLAGS
  [2ND_][CLANG_]TARGET_GLOBAL_CONLYFLAGS
  [2ND_][CLANG_]TARGET_GLOBAL_CPPFLAGS
  [2ND_][CLANG_]TARGET_GLOBAL_LDFLAGS

Many other variables are unnecessary now too, but those will be removed
in another change. For those we can ensure the build.ninja file does not
change, but we expect it to change here due to the ordering differences.

Change-Id: I0bd0778706d02ee27b2784dd8dc6b2c71d37bd3a