rdmd: support --eval <arg> to make it Makefile friendly

changelog/rdmdMakefiles.dd

@@ -0,0 +1,12 @@
+rdmd can now be used as a shell in makefiles
+
+With gnu make(3.82 or higher), rdmd can now be used in makefiles.
+This is accomplished by setting the SHELL and .SHELLFLAGS to /usr/bin/rdmd and --eval respectively.
+---
+.ONESHELL:
+SHELL = /usr/bin/rdmd
+.SHELLFLAGS = --eval
+hello.txt:
+$(TAB)import std.file;
+$(TAB)write("$@","hello world\n");
+---

rdmd.d

@@ -329,12 +329,14 @@ int main(string[] args)
 
 size_t indexOfProgram(string[] args)
 {
-    foreach(i, arg; args[1 .. $])
+    foreach(i; 1 .. args.length)
     {
+        auto arg = args[i];
         if (!arg.startsWith('-', '@') &&
-                !arg.endsWith(".obj", ".o", ".lib", ".a", ".def", ".map", ".res"))
+                !arg.endsWith(".obj", ".o", ".lib", ".a", ".def", ".map", ".res") &&
+                args[i - 1] != "--eval")
         {
-            return i + 1;
+            return i;
         }
     }
 

rdmd_test.d

@@ -614,6 +614,29 @@ void runTests(string rdmdApp, string compiler, string model)
         res = execute(rdmdArgs ~ [src1]);
         assert(res.status == 1, res.output);
     }
+
+    {
+        import std.format : format;
+
+        auto textOutput = tempDir().buildPath("rdmd_makefile_test.txt");
+        if (exists(textOutput))
+        {
+            remove(textOutput);
+        }
+        enum makefileFormatter = `.ONESHELL:
+SHELL = %s
+.SHELLFLAGS = %-(%s %) --eval
+%s:
+	import std.file;
+	write("$@","hello world\n");`;
+        string makefileString = format!makefileFormatter(rdmdArgs[0], rdmdArgs[1 .. $], textOutput);
+        auto makefilePath = tempDir().buildPath("rdmd_makefile_test.mak");
+        std.file.write(makefilePath, makefileString);
+        auto make = environment.get("MAKE") is null ? "make" : environment.get("MAKE");
+        res = execute([make, "-f", makefilePath]);
+        assert(res.status == 0, res.output);
+        assert(std.file.read(textOutput) == "hello world\n");
+    }
 }
 
 void runConcurrencyTest(string rdmdApp, string compiler, string model)

travis.sh

@@ -10,8 +10,15 @@ set -uexo pipefail
 GDMD=$(find ~/dlang -type f -name "gdmd")
 LDMD2=$(find ~/dlang -type f -name "ldmd2")
 
-make -f posix.mak all DMD="$(which dmd)"
-make -f posix.mak test DMD="$(which dmd)" \
+curl https://ftp.gnu.org/gnu/make/make-4.2.tar.gz | tar -xz
+cd make-4.2
+./configure
+./build.sh
+cd ..
+export MAKE=$(pwd)/make-4.2/make
+
+$MAKE -f posix.mak all DMD="$(which dmd)"
+$MAKE -f posix.mak test DMD="$(which dmd)" \
     RDMD_TEST_COMPILERS=dmd,"$GDMD","$LDMD2" \
     VERBOSE_RDMD_TEST=1