Use absolute CONAN_HOME path in CI and docs

- Set CONAN_HOME to ${{ github.workspace }}/build/conan in workflow jobs
- Document local absolute-path export in DEVELOPMENT.md and hostlibs README

Author: chsbuffer

.github/workflows/build.yml

@@ -14,7 +14,7 @@ jobs:
   windows-hostlibs:
     runs-on: windows-2025-vs2026
     env:
-      CONAN_HOME: build/conan
+      CONAN_HOME: ${{ github.workspace }}/build/conan
     strategy:
       matrix:
         include:
@@ -84,7 +84,7 @@ jobs:
   windows-skia:
     runs-on: windows-2025-vs2026
     env:
-      CONAN_HOME: build/conan
+      CONAN_HOME: ${{ github.workspace }}/build/conan
     strategy:
       matrix:
         include:
@@ -129,7 +129,7 @@ jobs:
   windows-angle:
     runs-on: windows-2025-vs2026
     env:
-      CONAN_HOME: build/conan
+      CONAN_HOME: ${{ github.workspace }}/build/conan
     strategy:
       matrix:
         include:
@@ -261,7 +261,7 @@ jobs:
   linux-hostlibs:
     runs-on: ubuntu-latest
     env:
-      CONAN_HOME: build/conan
+      CONAN_HOME: ${{ github.workspace }}/build/conan
     needs:
       - linux-sysroot
 
@@ -337,7 +337,7 @@ jobs:
   linux-skia:
     runs-on: ubuntu-latest
     env:
-      CONAN_HOME: build/conan
+      CONAN_HOME: ${{ github.workspace }}/build/conan
     needs:
       - linux-sysroot
 

DEVELOPMENT.md

@@ -89,7 +89,7 @@ task build-hostlibs ARCH=arm64
 task build-hostlibs ARCH=x64 PGO=false  # no-pgo flavor
 ```
 
-Conan 的 cache 和 source 目录位于 `build/conan`。
+`CONAN_HOME` 设为 `build/conan` 的绝对路径。本地构建前先 `export CONAN_HOME=$(pwd)/build/conan`（或 PowerShell: `$env:CONAN_HOME = "$PWD\build\conan"`）。
 
 ### 2. 构建 SkiaSharp / HarfBuzzSharp
 

native/hostlibs/README.md

@@ -4,7 +4,7 @@ This Conan 2 recipe builds and packages the .NET Runtime apphost and single-file
 host static link inputs. `pgo=True` is the default package; set `pgo=False` for
 the Windows no-PGO flavor.
 
-On Windows, set `CONAN_HOME` to `build\conan` to avoid path-length issues. The
+Set `CONAN_HOME` to an absolute path (e.g. `$PWD/build/conan`). The
 Runtime build has deeply nested paths and long MSVC command lines.
 
 The deployer preserves the response-file-relative directory tree expected by the