Fix bugs in --clang-macro-fallback

This commit resolves a bug where -include was not respected and a bug
where -MMD was passed to the fallback translation unit which would cause
the dependency file to be overwritten with useless information about
temporary files.

bindgen-tests/one_header-another_header-precompile.h

@@ -0,0 +1,3 @@
+
+#include <one_header.h>
+#include <another_header.h>

bindgen/clang.rs

@@ -1916,7 +1916,6 @@ impl Drop for TranslationUnit {
 /// Translation unit used for macro fallback parsing
 pub(crate) struct FallbackTranslationUnit {
     file_path: String,
-    header_path: String,
     pch_path: String,
     idx: Box<Index>,
     tu: TranslationUnit,
@@ -1932,7 +1931,6 @@ impl FallbackTranslationUnit {
     /// Create a new fallback translation unit
     pub(crate) fn new(
         file: String,
-        header_path: String,
         pch_path: String,
         c_args: &[Box<str>],
     ) -> Option<Self> {
@@ -1954,7 +1952,6 @@ impl FallbackTranslationUnit {
         )?;
         Some(FallbackTranslationUnit {
             file_path: file,
-            header_path,
             pch_path,
             tu: f_translation_unit,
             idx: f_index,
@@ -1993,7 +1990,6 @@ impl FallbackTranslationUnit {
 impl Drop for FallbackTranslationUnit {
     fn drop(&mut self) {
         let _ = std::fs::remove_file(&self.file_path);
-        let _ = std::fs::remove_file(&self.header_path);
         let _ = std::fs::remove_file(&self.pch_path);
     }
 }

bindgen/lib.rs

@@ -348,6 +348,7 @@ impl Builder {
         }
 
         // Transform input headers to arguments on the clang command line.
+        self.options.fallback_clang_args = self.options.clang_args.clone();
         self.options.clang_args.extend(
             self.options.input_headers
                 [..self.options.input_headers.len().saturating_sub(1)]

bindgen/options/mod.rs

@@ -1234,6 +1234,11 @@ options! {
         // This field is handled specially inside the macro.
         as_args: ignore,
     },
+    /// The set of arguments to be passed straight through to Clang for the macro fallback code.
+    fallback_clang_args: Vec<Box<str>> {
+        methods: {},
+        as_args: ignore,
+    },
     /// Tuples of unsaved file contents of the form (name, contents).
     input_header_contents: Vec<(Box<str>, Box<str>)> {
         methods: {

file.d

@@ -0,0 +1,2 @@
+.macro_eval.o: /home/jbaublitz/bindgen-test/testheader.h \
+  /usr/include/libcryptsetup.h .macro_eval.c