TL;DR: cgo seems to look in the current working directory for includes in preference to directories specified with -I, regardless of whether the include is specified with <> or "". I expect that the current directory is searched for includes only when they're included with "".
There are four test cases:
* cangled - C only - import a header file with <>
* cquoted - C only - import a header file with ""
* goangled - cgo - import a header file with <>
* goquoted - cgo - import a header file with ""
Each test case directory has a file cstuff/cdata.h, which has a constant char *the_text = "this is from the embedded directory";. Each test case prints that constant out. There's also a system/cstuff/cdata.h which contains a different version of that constant: char *the_text = "this is from the system directory";.
$ cd cangled; gcc -I../system main.c; ./a.out
this is from the system directory
As expected - gcc does not search the current directory for includes specified with <>
$ cd cquoted; gcc -I../system main.c; ./a.out
this is from the embedded directory
As expected - gcc searches the current directory in preference to any -I flags for includes specified with ""
$ cd goquoted; go run main.go;
this is from the embedded directory
As expected - cgo resolves the include from the current directory because of the ""
$ cd goangled; go run main.go;
this is from the embedded directory
This is not what I expect; I expect that since the include is done with <>, that the current directory is not used to resolve it, and instead it should find the version in system/cstuff/cdata.h because of the -I flag.