Ported most of Makefile logic over

build.h

@@ -0,0 +1,26 @@
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+
+int env_is(char *env, char *target) {
+    char *val = getenv(env);
+    return val && !strcmp(val, target);
+}
+
+char *maybe(char *in) {
+    return in ? in : "";
+}
+
+char *or_else(char *in, char *otherwise) {
+    return in ? in : otherwise;
+}
+
+int run(const char *cmd, ...) {
+    char buf[2048];
+    va_list args;
+    va_start(args, cmd);
+    vsprintf(buf, cmd, args);
+    va_end(args);
+    printf("--> %s\n\n", buf);
+    return system(buf);
+}