INSTALL.md: add CMake examples for macOS and iOS

Closes #16095

docs/INSTALL.md

@@ -367,6 +367,15 @@ make -j8
 make install
 ```
 
+With CMake:
+
+```bash
+cmake . \
+  -DCMAKE_OSX_ARCHITECTURES=x86_64 \
+  -DCMAKE_OSX_DEPLOYMENT_TARGET=10.8 \
+  -DCMAKE_OSX_SYSROOT="$(xcrun --sdk macosx --show-sdk-path)"
+```
+
 The above command lines build curl for macOS platform with `x86_64`
 architecture and `10.8` as deployment target.
 
@@ -383,6 +392,15 @@ make -j8
 make install
 ```
 
+With CMake (3.16 or upper recommended):
+
+```bash
+cmake . \
+  -DCMAKE_SYSTEM_NAME=iOS \
+  -DCMAKE_OSX_ARCHITECTURES=arm64 \
+  -DCMAKE_OSX_DEPLOYMENT_TARGET=11.0
+```
+
 Another example for watchOS simulator for macs with Apple Silicon:
 
 ```bash