1. New build system

Reviewed-on: #1

example/c-sum-v2/sum.jdg

@@ -0,0 +1,82 @@
+// Smoke test for the structured build DSL. Same task as example/c-sum
+// (sum of N integers) but described declaratively — no shell strings,
+// no per-platform `if /I "%CC%"=="msvc"` branching. The compiler is
+// selected via the JUDGE_CC env variable set by the CI matrix.
+
+toolchains {
+    gcc   { platforms = "linux"             }
+    clang { platforms = "linux" "windows"   }
+    msvc  { platforms = "windows"           }
+}
+
+build_defaults {
+    language = "c"
+    standard = "c11"
+    sources  = "solution.c"
+    output   = "solution"
+    warnings = strict
+}
+
+build "release" {
+    profile = release
+}
+
+build "debug" {
+    profile = debug
+}
+
+build "sanitized" {
+    profile   = sanitized
+    sanitize  = "address" "undefined"
+    platforms = "linux"
+    compilers = "gcc" "clang"
+}
+
+build "debug-valgrind" {
+    profile   = debug
+    wrapper   = "valgrind --error-exitcode=99 --leak-check=full -q"
+    platforms = "linux"
+    compilers = "gcc"
+}
+
+timeout 5s
+normalize_crlf = true
+trim_trailing_ws = true
+
+group("basic") {
+    weight = 0.5
+
+    test("one number") {
+        stdin  = "1\n42\n"
+        stdout = "42\n"
+    }
+
+    test("three numbers") {
+        stdin  = "3\n1 2 3\n"
+        stdout = "6\n"
+    }
+
+    test("negatives") {
+        stdin  = "4\n-1 -2 3 5\n"
+        stdout = "5\n"
+    }
+
+    test("zero count") {
+        stdin  = "0\n"
+        stdout = "0\n"
+    }
+}
+
+group("edge") {
+    weight = 0.5
+
+    test("large sum fits in int64") {
+        stdin  = "3\n2000000000 2000000000 2000000000\n"
+        stdout = "6000000000\n"
+    }
+
+    test("multiline input") {
+        stdin  = "5\n10\n20\n30\n40\n50\n"
+        stdout = "150\n"
+    }
+}