Fix CI/CD: Add fallback for systems without pkg-config

- detect_fuse.sh now checks for pkg-config availability first
- Falls back to checking for header files in standard locations
- Makefile provides default CFLAGS when pkg-config unavailable
- Fixes build on minimal CI/CD environments

Fallback locations checked:
- /usr/include/fuse3/fuse.h (FUSE 3)
- /usr/local/include/fuse3/fuse.h (FUSE 3)
- /usr/include/fuse/fuse.h (FUSE 2)
- /usr/local/include/fuse/fuse.h (FUSE 2)

Makefile

@@ -19,11 +19,11 @@ else
 endif
 
 ifeq ($(FUSE_VERSION),FUSE3)
-    FUSE_CFLAGS := $(shell pkg-config --cflags fuse3)
+    FUSE_CFLAGS := $(shell pkg-config --cflags fuse3 2>/dev/null || echo "-I/usr/include/fuse3 -D_FILE_OFFSET_BITS=64")
     FUSE_LIBS := -lfuse3
     FUSE_USE_VERSION := 30
 else ifeq ($(FUSE_VERSION),FUSE2)
-    FUSE_CFLAGS := $(shell pkg-config --cflags fuse)
+    FUSE_CFLAGS := $(shell pkg-config --cflags fuse 2>/dev/null || echo "-I/usr/include/fuse -D_FILE_OFFSET_BITS=64")
     FUSE_LIBS := -lfuse
     FUSE_USE_VERSION := 26
 else

detect_fuse.sh

@@ -1,9 +1,24 @@
 #!/bin/bash
 # Detect FUSE version and set appropriate flags
 
-if pkg-config --exists fuse3; then
+# Check if pkg-config is available
+if ! command -v pkg-config >/dev/null 2>&1; then
+    # Fallback: check for header files
+    if [ -f /usr/include/fuse3/fuse.h ] || [ -f /usr/local/include/fuse3/fuse.h ]; then
+        echo "FUSE3"
+    elif [ -f /usr/include/fuse/fuse.h ] || [ -f /usr/local/include/fuse/fuse.h ]; then
+        echo "FUSE2"
+    else
+        echo "NONE"
+        exit 1
+    fi
+    exit 0
+fi
+
+# Use pkg-config if available
+if pkg-config --exists fuse3 2>/dev/null; then
     echo "FUSE3"
-elif pkg-config --exists fuse; then
+elif pkg-config --exists fuse 2>/dev/null; then
     echo "FUSE2"
 else
     echo "NONE"