nitc: use ccache again

c02e04291807cf97228068cc5b52f453d84ab37b unexpectedly disable ccache.
Since CC is set by default[1], the ?= attempt did never assign anything[2].

The solution is to assign unless if CC is set by another mean.
This can be done thanks to the origin function[3].

  [1]: https://www.gnu.org/software/make/manual/html_node/Implicit-Variables.html
  [2]: https://www.gnu.org/software/make/manual/html_node/Flavors.html
  [3]: https://www.gnu.org/software/make/manual/html_node/Origin-Function.html

Signed-off-by: Jean Privat <jean@pryen.org>

diff --git a/src/compiler/abstract_compiler.nit b/src/compiler/abstract_compiler.nit
index 31795fc..a3a0bc8 100644 (file)
--- a/src/compiler/abstract_compiler.nit
+++ b/src/compiler/abstract_compiler.nit
@@ -360,8 +360,12 @@ class MakefileToolchain
                var debug = toolcontext.opt_debug.value
 
                makefile.write """
-CC ?= ccache cc
-CXX ?= ccache c++
+ifeq ($(origin CC), default)
+        CC = ccache cc
+endif
+ifeq ($(origin CXX), default)
+        CXX = ccache c++
+endif
 CFLAGS ?= -g {{{if not debug then "-O2" else ""}}} -Wno-unused-value -Wno-switch -Wno-attributes -Wno-trigraphs
 CINCL =
 LDFLAGS ?=