Fix gcc include dot

mesonbuild/compilers/mixins/gnu.py

@@ -286,6 +286,8 @@ class GnuLikeCompiler(metaclass=abc.ABCMeta):
         return ['-c']
 
     def get_include_args(self, path: str, is_system: bool) -> typing.List[str]:
+        if not path:
+            path = '.'
         if is_system:
             return ['-isystem' + path]
         return ['-I' + path]

test cases/common/225 include_dir dot/meson.build

@@ -0,0 +1,8 @@
+project('Include Here', 'c')
+
+# The layout with the .h file in . and the .c files in src/ is critical to
+# tickle the bug #5847
+
+inc = include_directories('.')
+
+subdir('src')

test cases/common/225 include_dir dot/rone.h

@@ -0,0 +1 @@
+int rOne(void);

test cases/common/225 include_dir dot/src/main.c

@@ -0,0 +1,5 @@
+#include "rone.h"
+
+int main() {
+    return rOne();
+}

test cases/common/225 include_dir dot/src/meson.build

@@ -0,0 +1,6 @@
+t = executable(
+  'main',
+  ['main.c', 'rone.c'],
+  include_directories : inc,
+  implicit_include_directories : false,
+)

test cases/common/225 include_dir dot/src/rone.c

@@ -0,0 +1,3 @@
+int rOne(void) {
+    return 1;
+}