Use soong_ui directly, instead of make

This will use ckati instead of make for dumping variables, for
consistent makefile parsing. It may also sandbox executions, etc.

Also skip the legacy make wrapper to build, and use soong_ui instead.
The command line arguments are equivalent, but -j is no longer
necessary, we'll default to a sane value.

Test: bit -b framework
Change-Id: Idc2c9d1abe84b6b783b8702925de5493d47a4509
diff --git a/tools/bit/command.cpp b/tools/bit/command.cpp
index 1ff7c22..f95ea11 100644
--- a/tools/bit/command.cpp
+++ b/tools/bit/command.cpp
@@ -189,7 +189,7 @@
 int
 exec_with_path_search(const char* prog, char const* const* argv, char const* const* envp)
 {
-    if (prog[0] == '/') {
+    if (strchr(prog, '/') != NULL) {
         return execve(prog, (char*const*)argv, (char*const*)envp);
     } else {
         char* pathEnv = strdup(getenv("PATH"));