feat: use PIC code model for shared libraries, fix shared library bugs

programs/libs/libhello/Makefile

@@ -11,6 +11,8 @@ NM := $(TOOLCHAIN_PREFIX)nm
 STRIP := $(TOOLCHAIN_PREFIX)strip
 
 # Compiler flags: freestanding, no stdlib
+# Build as PIE so library-internal data references remain valid after the
+# kernel maps the image into a per-process library slot.
 override CXXFLAGS := \
     -std=gnu++20 \
     -g -O2 -pipe \
@@ -20,7 +22,7 @@ override CXXFLAGS := \
     -ffreestanding \
     -fno-stack-protector \
     -fno-stack-check \
-    -fno-PIC \
+    -fPIE \
     -fno-rtti \
     -fno-exceptions \
     -ffunction-sections \