build: avoid redefining _FORTIFY_SOURCE

Check if `-D_FORTIFY_SOURCE` was already passed via the CFLAGS environment
variable and only add the flag if not already present.

Fixes: ea046bd ("build: enable source fortification by default")
Signed-off-by: Jo-Philipp Wich <[email protected]>

Merge pull request #153 from jow-/lib-sort-object-support

lib: support object ordering in `uc_sort()`

Merge pull request #118 from jow-/fs-read-getdelim

fs: expose `getdelim()` functionality through `fd.read()`

examples: add module search path initialization and freeing

Since commit 3c168b5 ("vm, cli: move search path into global config...")
it is required to explicitly initialize the module search path in the
configuration structure for compile time module imports and run time
require operations to work.

Signed-off-by: Jo-Philipp Wich <[email protected]>

Merge pull request #99 from jow-/gc-control

Implement periodic GC

Merge pull request #91 from jow-/ubus-propagate-exceptions

ubus: end uloop on exceptions in managed code

Merge pull request #77 from jow-/lib-fix-index

lib: rework uc_index() implementation

syntax: implement support for ES6 template literals

Implement support for ECMAScript 6 template literals which allow simple
interpolation of variable values into strings without resorting to
`sprintf()` or manual string concatenation.

Signed-off-by: Jo-Philipp Wich <[email protected]>

treewide: move json-c compat shims into internal header file

Do not expose the json-c compat functions in ucode's public headers to
avoid clashes when building on systems with modern json-c.

Also remove some explicit json-c/json-c.h includes in places where it is
not needed.

Signed-off-by: Jo-Philipp Wich <[email protected]>

ci: debian: change path before attempting to invoke Git operations

Fixes: dfaf05a ("ci: debian: automatically update changelog from Git tag")
Signed-off-by: Jo-Philipp Wich <[email protected]>