Fallback to newly build dmd if no host compiler is available

Author: wilzbach

src/posix.mak

@@ -128,7 +128,18 @@ ifeq (,$(AUTO_BOOTSTRAP))
   HOST_DMD?=dmd
   HOST_DMD_PATH=$(abspath $(shell which $(HOST_DMD)))
   ifeq (,$(HOST_DMD_PATH))
-    $(error '$(HOST_DMD)' not found, get a D compiler or make AUTO_BOOTSTRAP=1)
+    # On some occasions, even though $(HOST_DC) is undefined, a DMD compiler
+    # can be found in $(GENERATED)
+    ifneq (,$(wildcard $G/dmd))
+      HOST_DMD:=$G/dmd
+    # Cross-compilation
+    else ifneq (,$(wildcard $(GENERATED)/$(OS)/$(BUILD)/64/dmd))
+      HOST_DMD:=$(GENERATED)/$(OS)/$(BUILD)/64/dmd
+    else ifneq (,$(wildcard $(GENERATED)/$(OS)/$(BUILD)/32/dmd))
+      HOST_DMD:=$(GENERATED)/$(OS)/$(BUILD)/32/dmd
+    else
+      $(error '$(HOST_DMD)' not found, get a D compiler or make AUTO_BOOTSTRAP=1)
+    endif
   endif
   HOST_DMD_RUN:=$(HOST_DMD)
 else