[DB] return resolved path when path cannot be made relative

Summary:
This makes it more obvious why infer would force a path to be absolute since we
base that decision on the resolved path. For instance:

```
$ mkdir foo
$ cd foo
$ ln -s ../examples goo
$ infer -- clang -c goo/hello.c
[...]
/home/jul/infer/examples/hello.c:14: error: NULL_DEREFERENCE
```

We see that the path is outside of the current directory clearly, whereas
before infer would report on "goo/hello.c".

Reviewed By: akotulski

Differential Revision: D4409579

fbshipit-source-id: 7172005

infer/src/base/SourceFile.ml

@@ -47,7 +47,7 @@ let from_abs_path fname =
   | None -> (
       match Utils.filename_to_relative ~root:models_dir_real fname_real with
       | Some path -> RelativeInferModel path
-      | None -> Absolute fname (* fname is absolute already *)
+      | None -> Absolute fname_real (* fname_real is absolute already *)
     )
 
 let curr_encoding = `Enc_crc

infer/tests/build_systems/cmake/Makefile

@@ -13,7 +13,7 @@ CMAKE_ANALYZE_DIR = $(CMAKE_DIR)/_build_infer
 
 ANALYZER = infer
 CLEAN_EXTRA = $(CMAKE_BUILD_DIR) $(CMAKE_ANALYZE_DIR)
-INFER_OPTIONS = --project-root $(CMAKE_DIR)
+INFER_OPTIONS = --project-root $(TESTS_DIR)
 SOURCES = $(CMAKE_DIR)/hello.c
 OBJECTS = $(CMAKE_BUILD_DIR)/CMakeFiles/Hello.dir/hello.c.o
 INFERPRINT_OPTIONS = --issues-tests
@@ -39,4 +39,4 @@ infer-out/report.json: $(SOURCES) $(CMAKE_DIR)/CMakeLists.txt $(CLANG_DEPS)
 	$(call silent_on_success,\
 	  $(INFER_BIN) -a $(ANALYZER) $(INFER_OPTIONS) -- $(MAKE) -C $(CMAKE_ANALYZE_DIR))
 #	cmake makes all paths absolute
-	@sed -i -e 's#$(abspath $(CMAKE_DIR))/##g' $@
+	@sed -i -e 's#$(abspath $(TESTS_DIR))/##g' $@

infer/tests/build_systems/cmake/issues.exp

@@ -1 +1 @@
-hello.c, test, 2, NULL_DEREFERENCE, [start of procedure test()]
+build_systems/codetoanalyze/hello.c, test, 2, NULL_DEREFERENCE, [start of procedure test()]

infer/tests/build_systems/codetoanalyze/cmake/hello.c

@@ -1 +1 @@
-../../../../../examples/hello.c
+../hello.c

infer/tests/build_systems/genrule/Makefile

@@ -30,6 +30,7 @@ genrule: $(ROOT_DIR)/buck-out/genruletest/gen/infer/tests/build_systems/genrule/
 $(ROOT_DIR)/buck-out/genruletest/gen/infer/tests/build_systems/genrule/module2/module2_infer/infer_out/report.json: \
   $(JAVA_DEPS) $(JAVA_SOURCE_FILES)
 	cd $(ROOT_DIR) && \
+    $(REMOVE_DIR) buck-out && \
 	$(call silent_on_success,\
 	INFER_BIN="$(INFER_BIN)" NO_BUCKD=1 GENERATE_INFER_GENRULES=1 \
 	buck build --config project.buck_out=buck-out/genruletest --no-cache //infer/tests/build_systems/genrule/module2:module2_infer)
@@ -38,4 +39,4 @@ $(ROOT_DIR)/buck-out/genruletest/gen/infer/tests/build_systems/genrule/module2/m
 infer-out/report.json: $(ROOT_DIR)/buck-out/genruletest/gen/infer/tests/build_systems/genrule/module2/module2_infer/infer_out/report.json
 	$(MKDIR_P) infer-out
 #	the report contains absolute paths
-	@sed -e 's#$(abspath $(ROOT_DIR))/##g' $< > $@
+	@sed -e 's#$(abspath $(TESTS_DIR))/##g' $< > $@

infer/tests/build_systems/genrule/issues.exp

@@ -1 +1 @@
-buck-out/genruletest/gen/infer/tests/build_systems/genrule/module2/module2_infer__srcs/Class2.java, void Class2.localNPE2(), 2, NULL_DEREFERENCE, [start of procedure localNPE2()]
+build_systems/genrule/module2/Class2.java, void Class2.localNPE2(), 2, NULL_DEREFERENCE, [start of procedure localNPE2()]